linux-kernel - Re: [ckrm-tech] [PATCH 7/7] containers (V7): Container interface to nsproxy subsystem

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Message-ID: <20070328152619.GA24301@sergelap.austin.ibm.com>
Date:	Wed, 28 Mar 2007 10:26:19 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Srivatsa Vaddagiri <vatsa@...ibm.com>
Cc:	sekharan@...ibm.com, ckrm-tech@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, xemul@...ru, rohitseth@...gle.com,
	pj@....com, ebiederm@...ssion.com, winget@...gle.com,
	containers@...ts.osdl.org, menage@...gle.com
Subject: Re: [ckrm-tech] [PATCH 7/7] containers (V7): Container interface to nsproxy subsystem

Quoting Srivatsa Vaddagiri (vatsa@...ibm.com):
> On Mon, Mar 26, 2007 at 04:57:55PM -0500, Serge E. Hallyn wrote:
> > That is still not true, see kernel/utsname:copy_utsname().
> > 
> > Now you might have run a userspace testcase in a kernel with
> > CONFIG_UTS_NS=n, which at the moment erroneously returns 0 rather than
> > -EINVAL when you clone(CLONE_NEWUTS).  But you didn't get a new uts
> > namespace, you were just lied to  :)
> 
> I think you are right here, in that CONFIG_UTS_NS was not turned on,
> although I was thinking it was on.
> 
> However as a result of this experiment, I found this anomaly:
> 
> - On a kernel with CONFIG_UTS_NS=n, a test which does
>   clone(CLONE_NEWUTS) works fine. clone() succeeds and the child
>   starts running with no error.
> - On the same kernel, if ns container hierarchy is mounted, then
>   the test fails. clone() returns failure and child is never created.
>   As soon as the ns container hierarchy is unmounted, the test works
>   again.
> 
> I would have expected a consistent behavior here, irrespective of
> whether ns hierarchy is mounted or not. Is this difference in behavior
> acceptable? Returning -EINVAL in copy_utsname() when CONFIG_UTS_NS=n, as
> you say above, would fix this anomaly.

Will, not would, fix the anomaly  :)

2.6.21-rc5-mm2 has the correct behavior.  Returning 0 was a bug.

thanks,
-serge
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