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

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Date:	Fri, 25 Apr 2008 12:47:27 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	"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

"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.


> 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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