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From: Andrei Vagin <avagin-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: "Eric W. Biederman"
	<ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>,
	Michael Kerrisk
	<mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Linux Containers
	<containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>,
	Linux API <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	linux-fsdevel
	<linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"criu-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org"
	<criu-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>,
	Serge Hallyn
	<serge.hallyn-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>
Subject: How to get an owning userns for a superblock
Date: Mon, 1 May 2017 17:05:56 -0700	[thread overview]
Message-ID: <CANaxB-zFNSjZYhBNJt_hAewrvi2=0RHQ_oY0mTinWe4=9P=ieA@mail.gmail.com> (raw)

Hello Everyone,

Now superblock has a reference to userns. Is there a way to discover
an owning userns for a superblock from user-space? In CRIU, we need
this information to dump and restore mount namespaces. For other
users, this information can be useful too to analyze and understand
the running system.

Recently we solved a similar problem for namespaces:
https://lkml.org/lkml/2016/7/6/158

In that case, we added two ioctl-s for nsfs files. Here we have a deal
regular files and I am not sure that adding a new ioctl for them is a
good idea.

Another way to solve a problem is use the kcmp() system call. We will
need to add two commands. One is to compare user namespaces and
another one is to compare a supper block userns with another userns.
The first command is required to create a sorted list of user
namespaces and the second command allows to find a proper userns in
this list.

Maybe someone has a better idea about this?

Thanks,
Andrei

                 reply	other threads:[~2017-05-02  0:05 UTC|newest]

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