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Re: [PATCH 5/5] kernfs: add exportfs operations

From Tejun Heo <tj@kernel.org>
Newsgroups linux.kernel
Subject Re: [PATCH 5/5] kernfs: add exportfs operations
Date 2017-05-24 19:50 +0200
Message-ID <tKIA2-5m6-31@gated-at.bofh.it> (permalink)
References (2 earlier) <tKcJQ-65-21@gated-at.bofh.it> <tKncd-77q-5@gated-at.bofh.it> <tKIqm-5iH-9@gated-at.bofh.it> <tKIA1-5m6-1@gated-at.bofh.it> <tKIA2-5m6-19@gated-at.bofh.it>
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Hello, Christoph.

On Wed, May 24, 2017 at 10:41:38AM -0700, Christoph Hellwig wrote:
> > But how do you map that back to the cgroup without scanning the cgroup
> > hierarchy?
> 
> I'm totally lost on why you would do that.  So maybe you just need
> to send the full patch so that reviewers get the full picture.

Here's a simple scenario.  Let's say blktrace now exposes the cgroup
inode and generation numbers per trace.  Userland tool now wants to
show that in a human readable format but it can only map back the
inode and generation numbers to the path by scanning the cgroup tree.
So, the goal is having a token which is not path which uniquely
identifies a cgroup and the ability to map that back to cgroup path.
We can add a dedicated interface to cgroup root, for example, and
allow querying by echoing inode and generation numbers into it but
that's kinda clumsy.

Thanks.

-- 
tejun

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Thread

[PATCH 5/5] kernfs: add exportfs operations Shaohua Li <shli@fb.com> - 2017-05-23 01:00 +0200
  Re: [PATCH 5/5] kernfs: add exportfs operations Christoph Hellwig <hch@infradead.org> - 2017-05-23 09:50 +0200
    Re: [PATCH 5/5] kernfs: add exportfs operations Tejun Heo <tj@kernel.org> - 2017-05-23 21:00 +0200
      Re: [PATCH 5/5] kernfs: add exportfs operations Christoph Hellwig <hch@infradead.org> - 2017-05-24 19:40 +0200
        Re: [PATCH 5/5] kernfs: add exportfs operations Tejun Heo <tj@kernel.org> - 2017-05-24 19:50 +0200
          Re: [PATCH 5/5] kernfs: add exportfs operations Christoph Hellwig <hch@infradead.org> - 2017-05-24 19:50 +0200
            Re: [PATCH 5/5] kernfs: add exportfs operations Tejun Heo <tj@kernel.org> - 2017-05-24 19:50 +0200
  Re: [PATCH 5/5] kernfs: add exportfs operations Tejun Heo <tj@kernel.org> - 2017-05-23 21:00 +0200

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