linux-kernel - Re: [RFC v2 1/2] kernel/sysctl: support setting sysctl parameters from kernel command line

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Message-ID: <20200326133915.GQ27965@dhcp22.suse.cz>
Date:   Thu, 26 Mar 2020 14:39:15 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Christian Brauner <christian.brauner@...ntu.com>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        linux-mm@...ck.org, Ivan Teterevkov <ivan.teterevkov@...anix.com>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        "Guilherme G . Piccoli" <gpiccoli@...onical.com>
Subject: Re: [RFC v2 1/2] kernel/sysctl: support setting sysctl parameters
 from kernel command line

On Thu 26-03-20 14:30:41, Christian Brauner wrote:
> On Thu, Mar 26, 2020 at 07:58:29AM +0100, Michal Hocko wrote:
> > On Wed 25-03-20 17:20:40, Eric W. Biederman wrote:
> > > Vlastimil Babka <vbabka@...e.cz> writes:
> > [...]
> > > > +	if (strncmp(param, "sysctl.", sizeof("sysctl.") - 1))
> > > > +		return 0;
> > > 
> > > Is there any way we can use a slash separated path.  I know
> > > in practice there are not any sysctl names that don't have
> > > a '.' in them but why should we artifically limit ourselves?
> > 
> > Because this is the normal userspace interface? Why should it be any
> > different from calling sysctl?
> > [...]
> 
> Imho, we should use ".". Kernel developers aren't the ones setting
> these options, admins are and if I think back to the times doing that as
> a job at uni I'd be very confused if I learned that I get to set sysctl
> options through the kernel command but need to use yet another format
> than what I usually do to set those from the shell. Consistency is most
> of the times to be preferred imho.

Absolutely agreed! Even if sysctl can consume / instead of ., which was a
news to me btw, the majority of the usage is with `.'
-- 
Michal Hocko
SUSE Labs