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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 8904BC2BA19 for ; Wed, 15 Apr 2020 09:04:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6435E206E9 for ; Wed, 15 Apr 2020 09:04:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586941470; bh=6Uf+FHmo8nvRfSiHPdrZgA/7AJpQX7o1hOkc3xcNH5Y=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=Tvu6hW/wm+VehR0a/OgXDPPR8YXrZwPuU9LaSCs6cpMhh/batl8mAN5LhaxuqOD87 KebddauTI0nKcRj/yiEi6CsAc/qB98+BqK8ZOAqhI6PLS8Hnfq8n2MKGY0T2GSVRxt 21JYhZiMSWLEOa9rsK+4G8CIOje+HYnNGreMq+CI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393836AbgDOJEV (ORCPT ); Wed, 15 Apr 2020 05:04:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:55104 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390645AbgDOJEC (ORCPT ); Wed, 15 Apr 2020 05:04:02 -0400 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 98A0120775; Wed, 15 Apr 2020 09:03:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586941441; bh=6Uf+FHmo8nvRfSiHPdrZgA/7AJpQX7o1hOkc3xcNH5Y=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=whw9AE1FcCYHqiqYow7YdaN0KuUEpYhHQmobiTs2rs34TaCZrbGc+BCL5rwKSJJQx 0xvzItctDZoQc90DshDkCR1jfedSWYbvNDvDOXWDHI/NCRnEGyvssM+5XtRsfRFd0f vwpw6v/8zFe88LhTTbrQmJb0U2YE2DJfJzVCSEwU= Date: Wed, 15 Apr 2020 18:03:55 +0900 From: Masami Hiramatsu To: Vlastimil Babka Cc: Andrew Morton , 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 Subject: Re: [PATCH v2 1/3] kernel/sysctl: support setting sysctl parameters from kernel command line Message-Id: <20200415180355.00bc828ea726c421638db871@kernel.org> In-Reply-To: <20200414113222.16959-2-vbabka@suse.cz> References: <20200414113222.16959-1-vbabka@suse.cz> <20200414113222.16959-2-vbabka@suse.cz> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 14 Apr 2020 13:32:20 +0200 Vlastimil Babka wrote: > A recently proposed patch to add vm_swappiness command line parameter in > addition to existing sysctl [1] made me wonder why we don't have a general > support for passing sysctl parameters via command line. Googling found only > somebody else wondering the same [2], but I haven't found any prior discussion > with reasons why not to do this. > > Settings the vm_swappiness issue aside (the underlying issue might be solved in > a different way), quick search of kernel-parameters.txt shows there are already > some that exist as both sysctl and kernel parameter - hung_task_panic, > nmi_watchdog, numa_zonelist_order, traceoff_on_warning. A general mechanism > would remove the need to add more of those one-offs and might be handy in > situations where configuration by e.g. /etc/sysctl.d/ is impractical. > > Hence, this patch adds a new parse_args() pass that looks for parameters > prefixed by 'sysctl.' and tries to interpret them as writes to the > corresponding sys/ files using an temporary in-kernel procfs mount. This > mechanism was suggested by Eric W. Biederman [3], as it handles all dynamically > registered sysctl tables, even though we don't handle modular sysctls. Errors > due to e.g. invalid parameter name or value are reported in the kernel log. > > The processing is hooked right before the init process is loaded, as some > handlers might be more complicated than simple setters and might need some > subsystems to be initialized. At the moment the init process can be started and > eventually execute a process writing to /proc/sys/ then it should be also fine > to do that from the kernel. > > Sysctls registered later on module load time are not set by this mechanism - > it's expected that in such scenarios, setting sysctl values from userspace is > practical enough. > > [1] https://lore.kernel.org/r/BL0PR02MB560167492CA4094C91589930E9FC0@BL0PR02MB5601.namprd02.prod.outlook.com/ > [2] https://unix.stackexchange.com/questions/558802/how-to-set-sysctl-using-kernel-command-line-parameter > [3] https://lore.kernel.org/r/87bloj2skm.fsf@x220.int.ebiederm.org/ > > Signed-off-by: Vlastimil Babka > Reviewed-by: Luis Chamberlain [...] > diff --git a/init/main.c b/init/main.c > index a48617f2e5e5..7b43118215d6 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -1372,6 +1372,8 @@ static int __ref kernel_init(void *unused) > > rcu_end_inkernel_boot(); > > + do_sysctl_args(); > + Ah, I see. Since the sysctl is designed to be called after all __init calls were done, it shouldn't use bootconfig directly because bootconfig is full of __init call. OK, anyway we can use "kernel.sysctl" prefixed bootconfig for these. Reviewed-by: Masami Hiramatsu Thank you, -- Masami Hiramatsu