Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount

From: Eric W. Biederman
Date: Wed Feb 15 2017 - 04:44:31 EST

Djalal Harouni <tixxdz@xxxxxxxxx> writes:

> On Mon, Feb 13, 2017 at 11:15 AM, Eric W. Biederman
> <ebiederm@xxxxxxxxxxxx> wrote:
>> James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> writes:

>>> So is this. Basically anything that begins by mounting gets a super
>>> block and can use the s_user_ns to map from the filesystem view to the
>>> kernel view of ids. Apart from greater sophistication in the
>>> parametrisation, it sounds like we have all the machinery you need.
>>> I'm sure the containers people will consider reasonable patches to
>>> change this.
>> Yes.
>> And to be clear we have all of that merged now and mostly present and
>> hooked up in all filesystems without any shiftfs like changes needed.
>> To use this with a filesystem a last pass needs to be had to verify that
>> the cases where something does not map are handled cleanly.
> Still this does not answer the question how to dynamically
> *attach/share* data or read-only volumes as defined by
> orchestration/container tools into several containers. Am I missing
> something or is the plan to have per superblock mount for each one ?

Agreed. That is a related problem and the problem that shiftfs
is working to solve.

If you only need a single mapping the infrastructure is basically done
in the kernel today. If you need multiple mappings we need something