Date: Thu, 26 Nov 2015 23:25:11 -0600
From: "Serge E. Hallyn" <serge.hallyn@ubuntu.com>
To: Tejun Heo <tj@kernel.org>
Cc: serge@hallyn.com, linux-kernel@vger.kernel.org, adityakali@google.com,
        linux-api@vger.kernel.org, containers@lists.linux-foundation.org,
        cgroups@vger.kernel.org, lxc-devel@lists.linuxcontainers.org,
        akpm@linux-foundation.org, ebiederm@xmission.com
Subject: Re: [PATCH 1/8] kernfs: Add API to generate relative kernfs path
Message-ID: <20151127052511.GA25490@mail.hallyn.com>
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On Tue, Nov 24, 2015 at 11:16:30AM -0500, Tejun Heo wrote:
> Hello,
> 
> On Mon, Nov 16, 2015 at 01:51:38PM -0600, serge@hallyn.com wrote:
> > +static char * __must_check kernfs_path_from_node_locked(

(Note I've rewritten this to find a common ancestor and walk back to
and from that, as you suggested later in this email)

> > +	/* Short-circuit the easy case - kn_to is the root node. */
> > +	if ((kn_from == kn_to) || (!kn_from && !kn_to->parent)) {
> > +		*p = '/';
> > +		*(p + 1) = '\0';
> 
> Hmm... so if kn_from == kn_to, the output is "/"?

Yes, that's what seems to make the most sense for cgroup namespaces.  I
could see a case for '.' being used instead in general, but for cgroup
namespaces I think we'd have to convert those back to '/'.  Otherwise
we'll fail in being able to run legacy software, which would get
confused.

-serge
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