linux-kernel - Re: [RFC][PATCH 0/7] Clone PTS namespace

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Message-ID: <20080426130243.GA8591@sergelap.austin.ibm.com>
Date:	Sat, 26 Apr 2008 08:02:43 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"Serge E. Hallyn" <serue@...ibm.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Containers <containers@...ts.osdl.org>, clg@...ibm.com,
	linux-kernel@...r.kernel.org, Pavel Emelyanov <xemul@...nvz.org>,
	Benjamin Thery <benjamin.thery@...l.net>
Subject: Re: [RFC][PATCH 0/7] Clone PTS namespace

Quoting Eric W. Biederman (ebiederm@...ssion.com):
> "Serge E. Hallyn" <serue@...ibm.com> writes:
> 
> 
> > Heh, well I tried several approaches - adding tag_ops to kset, to ktype,
> > etc.  Finally ended up just calling sysfs_enable_tagging on
> > /sys/kernel/uids when that is created.  It's now working perfectly.
> 
> Sounds good.
> 
> >> I suspect since you are working on this and I seem to be stuck
> >> in molasses at the moment it makes sense to figure out what it
> >> will take to handle the uid namespace before pushing these
> >> patches again.
> >
> > I had ported your patches to 2.6.25, but Benjamin in the meantime ported
> > them to 2.6.25-mm1.  Since that's closer to the -net tree it's a more
> > useful port, so I'll let him post his patchset.  Then I'll send the
> > userns patch on top of that.  While I'm not actually able to send
> > network traffic over a veth dev (I probably am still not setting it up
> > right), I am able to pass veth devices into network namespaces, and the
> > user namespaces are properly handled.
> >
> > I believe Benjamin did notice a problem with some symlinks not existing,
> > and I think we want one more patch on top of yours removing the
> > hold_net() from sysfs_mount, which I don't think was what you really
> > wanted to do.  By simply removing that, if all tasks in a netns go away,
> > the netns actually goes away and a lookup under a bind-mounted copy of
> > its /sys/class/net is empty.
> 
> I will have to look, I need to refresh myself on where all of this code is.
> I think hold_net was what I wanted.  A record that there is a user
> but not something that will keep the network namespace from going away.
> 
> Essentially hold_net should be a debugging check rather then a
> real limitation.

Ah, I see, I assumed it actually pinned it.  Sorry, never mind then  :)

-serge

> > Anyway the patches should be hitting the list next week.
> 
> Cool.  We can figure out what we need to do to merge them from
> there.
> 
> >> Taking a quick look and having a clue what we will need to
> >> do for a theoretical device namespace is also a possibility.
> >
> > I'm not sure I'm familiar enough with the kobject/class/sysfs/device
> > relationships yet to comment on that.  It doesn't look like it should
> > really be a problem, though simply adding tags to every directory
> > under /sys/class (/sys/class/tty, /sys/class/usb_device, etc) doesn't
> > seem like necessarily the nicest way to go...
> 
> True.  And the goal is something maintainable.  There are still a lot
> of implications of a device namespace left unexamined so we shall see.
> 
> Eric
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