Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces
From: Andrew Vagin
Date: Mon Jul 25 2016 - 22:08:04 EST
On Sun, Jul 24, 2016 at 12:10:21AM -0500, Eric W. Biederman wrote:
> Andrey Vagin <avagin@xxxxxxxxxx> writes:
> > Hello,
> > I forgot to add --cc-cover for git send-email, so everyone who is in
> > Cc got only a cover letter. All messages were sent in mail lists.
> > Sorry for inconvenience.
> Mostly the code looked sensible. But I had a couple of issues.
> Resend this in September (when the merge window is closed and I am back
> from vacation) and I will give this a thorough review and get this
> merged. Or possibly next week if Linus releases another -rc
Eric, thank you for the detailed comments. I will rework this series and
send it after the merge window.
> > On Thu, Jul 14, 2016 at 11:20 AM, Andrey Vagin <avagin@xxxxxxxxxx> wrote:
> >> Each namespace has an owning user namespace and now there is not way
> >> to discover these relationships.
> >> Pid and user namepaces are hierarchical. There is no way to discover
> >> parent-child relationships too.
> >> Why we may want to know relationships between namespaces?
> >> One use would be visualization, in order to understand the running system.
> >> Another would be to answer the question: what capability does process X have to
> >> perform operations on a resource governed by namespace Y?
> >> One more use-case (which usually called abnormal) is checkpoint/restart.
> >> In CRIU we age going to dump and restore nested namespaces.
> >> There  was a discussion about which interface to choose to determing
> >> relationships between namespaces.
> >> Eric suggested to add two ioctl-s :
> >>> Grumble, Grumble. I think this may actually a case for creating ioctls
> >>> for these two cases. Now that random nsfs file descriptors are bind
> >>> mountable the original reason for using proc files is not as pressing.
> >>> One ioctl for the user namespace that owns a file descriptor.
> >>> One ioctl for the parent namespace of a namespace file descriptor.
> >> Here is an implementaions of these ioctl-s.
> >>  https://lkml.org/lkml/2016/7/6/158
> >>  https://lkml.org/lkml/2016/7/9/101
> >> Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
> >> Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> >> Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@xxxxxxxxx>
> >> Cc: "W. Trevor King" <wking@xxxxxxxxxx>
> >> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> >> Cc: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>