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From: ebiederm@xmission.com (Eric W. Biederman)
To: Djalal Harouni <tixxdz@gmail.com>
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Date: Wed, 15 Feb 2017 22:37:41 +1300
In-Reply-To: <CAEiveUfq1BWmHyPabD7gW4RbxszKUEbXy8Q9=7g4-PCC1P3fQA@mail.gmail.com>
        (Djalal Harouni's message of "Wed, 15 Feb 2017 10:33:53 +0100")
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Subject: Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount
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Djalal Harouni <tixxdz@gmail.com> writes:

> On Mon, Feb 13, 2017 at 11:15 AM, Eric W. Biederman
> <ebiederm@xmission.com> wrote:
>> James Bottomley <James.Bottomley@HansenPartnership.com> 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
more.

Eric