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

Andrew Vagin
2016-07-10T05:36:38Z

On Fri, Jul 08, 2016 at 10:13:08PM -0500, Eric W. Biederman wrote:
> "W. Trevor King" <wking@tremily.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
>
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