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

From	Amir Goldstein <amir73il@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount
Date	2017-02-07 22:10 +0100
Message-ID	<t8lbs-81u-7@gated-at.bofh.it> (permalink)
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On Tue, Feb 7, 2017 at 10:05 PM, James Bottomley
<James.Bottomley@hansenpartnership.com> wrote:
> On Tue, 2017-02-07 at 11:49 -0800, Christoph Hellwig wrote:
>> On Tue, Feb 07, 2017 at 11:02:03AM -0800, James Bottomley wrote:
>> > >   Another option would be to require something like a project as
>> > > used
>> > > for project quotas as the root.  This would also be conveniant as
>> > > it
>> > > could storge the used remapping tables.
>> >
>> > So this would be like the current project quota except set on a
>> > subtree?  I could see it being done that way but I don't see what
>> > advantage it has over using flags in the subtree itself (the
>> > mapping is
>> > known based on the mount namespace, so there's really only a single
>> > bit
>> > of information to store).
>>
>> projects (which are the underling concept for project quotas) are
>> per-subtree in practice - the flag is set on an inode and then
>> all directories and files underneath inherit the project ID,
>> hardlinking outside a project is prohinited.
>
> OK, this is what I don't understand: how is something that's inode
> based limited to be per-subtree?  The way I've seen the VFS operate it
> seems that any given inode (and indeed dentry) can appear in many
> subtrees so how do I limit them to just one?
>

Project id's are not exactly "subtree" semantic, but inheritance semantics,
which is not the same when non empty directories get their project id changed.
Here is a recap:
https://lwn.net/Articles/623835/

So if you created an empty directory and "marked" it for shiftuid and all
descendants inherited this property you would be able to check that property
on a per inode basis. Not sure that is what you are looking for?
I guess we should define the semantics for the required sub-tree marking,
before we can talk about solutions.

Thread

Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-04 20:20 +0100
  Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Amir Goldstein <amir73il@gmail.com> - 2017-02-05 09:00 +0100
    Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-06 02:20 +0100
      Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Amir Goldstein <amir73il@gmail.com> - 2017-02-06 08:00 +0100
        Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-06 15:50 +0100
  Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount "J. R. Okajima" <hooanon05g@gmail.com> - 2017-02-06 04:30 +0100
    Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Amir Goldstein <amir73il@gmail.com> - 2017-02-06 07:40 +0100
      Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-06 17:40 +0100
    Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-06 07:50 +0100
      Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Theodore Ts'o <tytso@mit.edu> - 2017-02-06 16:00 +0100
        Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-06 16:20 +0100
          Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount lkml@pengaru.com - 2017-02-06 16:40 +0100
            Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-06 18:40 +0100
          Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount bfields@fieldses.org (J. Bruce Fields) - 2017-02-06 23:00 +0100
            Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-07 01:20 +0100
              Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount "J. Bruce Fields" <bfields@fieldses.org> - 2017-02-07 02:40 +0100
                Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-07 20:10 +0100
                Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Christoph Hellwig <hch@infradead.org> - 2017-02-07 20:50 +0100
      Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount "J. R. Okajima" <hooanon05g@gmail.com> - 2017-02-06 17:30 +0100
  Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Christoph Hellwig <hch@infradead.org> - 2017-02-07 10:20 +0100
    Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Djalal Harouni <tixxdz@gmail.com> - 2017-02-07 10:40 +0100
      Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Christoph Hellwig <hch@infradead.org> - 2017-02-07 11:00 +0100
    Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-07 17:40 +0100
      Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Amir Goldstein <amir73il@gmail.com> - 2017-02-07 19:00 +0100
        Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Christoph Hellwig <hch@infradead.org> - 2017-02-07 19:20 +0100
          Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-07 20:10 +0100
            Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Christoph Hellwig <hch@infradead.org> - 2017-02-07 21:00 +0100
              Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-07 21:10 +0100
                Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Amir Goldstein <amir73il@gmail.com> - 2017-02-07 22:10 +0100
                Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Christoph Hellwig <hch@infradead.org> - 2017-02-07 23:50 +0100
                Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-08 00:50 +0100
                Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Amir Goldstein <amir73il@gmail.com> - 2017-02-08 08:00 +0100
                Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Konstantin Khlebnikov <khlebnikov@yandex-team.ru> - 2017-02-08 13:10 +0100
                Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-08 16:00 +0100
                Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-08 16:30 +0100
              Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Josh Triplett <josh@joshtriplett.org> - 2017-02-08 03:00 +0100
                Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-08 16:30 +0100
                Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Josh Triplett <josh@joshtriplett.org> - 2017-02-09 11:40 +0100
                Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-09 17:40 +0100
                Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount ebiederm@xmission.com (Eric W. Biederman) - 2017-02-13 11:30 +0100
        Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-07 19:30 +0100
          Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Djalal Harouni <tixxdz@gmail.com> - 2017-02-07 20:50 +0100

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