linux-kernel - Re: [CRIU] Introspecting userns relationships to other namespaces?

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Message-ID: <20160710053609.GB4868@outlook.office365.com>
Date:	Sat, 9 Jul 2016 22:36:11 -0700
From:	Andrew Vagin <avagin@...tuozzo.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	"W. Trevor King" <wking@...mily.us>, <criu@...nvz.org>,
	Linux API <linux-api@...r.kernel.org>,
	Containers <containers@...ts.linux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
	"Serge E. Hallyn" <serge@...lyn.com>
Subject: Re: [CRIU] Introspecting userns relationships to other namespaces?

On Fri, Jul 08, 2016 at 10:13:08PM -0500, Eric W. Biederman wrote:
> "W. Trevor King" <wking@...mily.us> writes:
> 
> > On Thu, Jul 07, 2016 at 08:01:52AM -0700, James Bottomley wrote:
> >> In theory, we could get nsfs to show this information as an option
> >> (just add a show_options entry to the superblock ops), but the
> >> problem is that although each namespace has a parent user_ns,
> >> there's no way to get it without digging in the namespace specific
> >> structure.  Probably we should restructure to move it into
> >> ns_common, then we could display it (and enforce all namespaces
> >> having owning user_ns) but it would be a reasonably large (but
> >> mechanical) change.
> >
> > It sounds like everyone is either positive or or neutral on this
> > groundwork, even if we haven't decided if/how to expose the
> > information to userspace.  I'm happy to work up a patch while the rest
> > of the discussion continues.  I'm also happy to let someone else work
> > up the patch, if anyone else is chomping at the bit ;).
> 
> I am dubious on moving all of the user namespace members into ns_common.
> 
> I would happy to be proved wrong but I suspect in the cases where we
> actually use that user namespace the code will become uglier.  Making
> the ordinary uses uglier to make a rare corner case nicer is the wrong
> trade off.
> 
> But feel free to try it is certainly worth doing if it doesn't make the
> code that uses the user namespaces uglier.

If it's interesting for someone, I have this patch in my tree
https://github.com/avagin/linux-task-diag/commit/63b32df68ae8d3a3842bae42bbcae3468db76d85

I can't say that it makes something uglier.

> 
> Eric
> 
> _______________________________________________
> CRIU mailing list
> CRIU@...nvz.org
> https://lists.openvz.org/mailman/listinfo/criu

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