Date: Mon, 2 Dec 2013 00:12:33 -0800
From: Christoph Hellwig <hch@infradead.org>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>, linux-nfs@vger.kernel.org,
        linux-fsdevel@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Eric Biederman <ebiederm@xmission.com>
Subject: Re: [PATCH 00/11] [RFC] repair net namespace damage to rpc_pipefs
Message-ID: <20131202081233.GA6953@infradead.org>
References: <20131201131441.790963326@bombadil.infradead.org>
 <20131201181329.GC10323@ZenIV.linux.org.uk>
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On Sun, Dec 01, 2013 at 06:13:29PM +0000, Al Viro wrote:
> Making the series no-go in that form, obviously.

Looking at the mess it made I'd almost be tempted to say a little leak
for a less used features is better than lots of pain for everyone..

Looking at the mess it made I'm really upset.

> > Given that the namespace kraken has infected various internal filesystem
> > and will get more soon I suspect this problem is or will become generic
> > and will need a proper solution anyway.  Al, any good ideas how to deal
> > with this?  Most straight forward way would be to add a counter of
> > user vfsmount to the superblock and methods when it goes to 1 and 0,
> > but that seems a bit ugly.
> 
> Folks, please, _please_, let's formulate the lifecycle rules first; we
> already had way too much trouble from putting mechanism first only to
> run into questions like the above ("what happens if somebody tries to
> allocate a PID in pid_ns that is already scheduled for shutdown?").
> Remember the (recurring) fun with kobject-related lifetime issues?
> Or rpc_pipefs notifier ugliness, for that matter...

I'll have to let the net namespace folks chime in for that, as far as
I'm concerned it's a featured better config'ed off.  If they can't come
up with anything better the procfs hack above would be it.