linux-kernel - Re: [PATCH 5/8] kernfs: let objects opt-in to propagating from the initial namespace

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Date:   Mon, 13 Apr 2020 15:02:39 -0400
From:   Tejun Heo <tj@...nel.org>
To:     Christian Brauner <christian.brauner@...ntu.com>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-api@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        Serge Hallyn <serge@...lyn.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Saravana Kannan <saravanak@...gle.com>,
        Jan Kara <jack@...e.cz>, David Howells <dhowells@...hat.com>,
        Seth Forshee <seth.forshee@...onical.com>,
        David Rheinsberg <david.rheinsberg@...il.com>,
        Tom Gundersen <teg@...m.no>,
        Christian Kellner <ckellner@...hat.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Stéphane Graber <stgraber@...ntu.com>,
        linux-doc@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 5/8] kernfs: let objects opt-in to propagating from the
 initial namespace

Hello,

On Wed, Apr 08, 2020 at 05:21:48PM +0200, Christian Brauner wrote:
> The initial namespace is special in many ways. One feature it always has
> had is that it propagates all its devices into all non-initial
> namespaces. This is e.g. true for all device classes under /sys/class/

Maybe I'm missing your point but I've always thought of it the other way
around. Some namespaces make all objects visible in init_ns so that all
non-init namespaces are subset of the init one, which sometimes requires
creating aliases. Other namespaces don't do that. At least in my experience,
the former is a lot easier to administer.

The current namespace support in kernfs behaves the way it does because the
only namespace it supports is netns, but if we're expanding it, I think it
might be better to default to init_ns is superset of all others model and make
netns opt for the disjointing behavior.

Thanks.

-- 
tejun