From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2C4DEC83007 for ; Tue, 28 Apr 2020 08:09:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0BB53206B9 for ; Tue, 28 Apr 2020 08:09:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726815AbgD1IJl (ORCPT ); Tue, 28 Apr 2020 04:09:41 -0400 Received: from mx2.suse.de ([195.135.220.15]:50810 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726377AbgD1IJl (ORCPT ); Tue, 28 Apr 2020 04:09:41 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id DF892AD0E; Tue, 28 Apr 2020 08:09:37 +0000 (UTC) Subject: Re: [PATCH v3 1/5] kernel/sysctl: support setting sysctl parameters from kernel command line To: Andrew Morton Cc: Luis Chamberlain , Kees Cook , Iurii Zaikin , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-mm@kvack.org, Ivan Teterevkov , Michal Hocko , David Rientjes , Matthew Wilcox , "Eric W . Biederman" , "Guilherme G . Piccoli" , Alexey Dobriyan , Thomas Gleixner , Greg Kroah-Hartman , Christian Brauner , Masami Hiramatsu , Michal Hocko References: <20200427180433.7029-1-vbabka@suse.cz> <20200427180433.7029-2-vbabka@suse.cz> <20200427113331.f0c1e8e7cee98644260448d3@linux-foundation.org> From: Vlastimil Babka Message-ID: Date: Tue, 28 Apr 2020 10:09:37 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200427113331.f0c1e8e7cee98644260448d3@linux-foundation.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/27/20 8:33 PM, Andrew Morton wrote: > On Mon, 27 Apr 2020 20:04:29 +0200 Vlastimil Babka wrote: > >> ... >> >> + sysctl.*= [KNL] >> + Set a sysctl parameter, right before loading the init >> + process, as if the value was written to the respective >> + /proc/sys/... file. Both '.' and '/' are recognized as >> + separators. Unrecognized parameters and invalid values >> + are reported in the kernel log. Sysctls registered >> + later by a loaded module cannot be set this way. >> + Example: sysctl.vm.swappiness=40 > > Why support "."? I think only supporting "/" is perfectly adequate and > simplifies documentation. It aligns the command-line syntax with the > rest of the sysctl documentation. I'm not seeing the need to provide > two ways of doing the same thing? AFAIK the "." is traditional, and "/" is a newer artefact of moving from the binary syscall form to procfs based form. So by "command-line syntax" you mean echo and cat, not sysctl tool? Because "man sysctl" says: variable The name of a key to read from. An example is kernel.ostype. The '/' separator is also accepted in place of a '.'. So I'm not strongly against supporting only / but I expect most people are used to the . and it will take them two attempts to pass the sysctl boot parameter correctly if they don't use it regularly - first trying . form, wonder why it doesn't work, then read the doc and realize it's not supported? Vlastimil