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

From	Vivek Goyal <vgoyal@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount
Date	2017-02-20 20:30 +0100
Message-ID	<td1OO-kv-11@gated-at.bofh.it> (permalink)
References	(3 earlier) <tbwDn-8mJ-9@gated-at.bofh.it> <tbGW5-6FB-5@gated-at.bofh.it> <tbUFH-7gh-5@gated-at.bofh.it> <tbXDA-DC-21@gated-at.bofh.it> <tcqme-296-9@gated-at.bofh.it>
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On Sat, Feb 18, 2017 at 07:24:38PM -0800, James Bottomley wrote:

[..]
> > > Yes, this is a known characteristic of stacked filesystems.  Is 
> > > there some magic I don't know about that would make it easier to 
> > > reflect hard links as aliases?
> > 
> > I think overlayfs had the same issue in the beginning and miklos
> > fixed it.
> > 
> > commit 51f7e52dc943468c6929fa0a82d4afac3c8e9636
> > Author: Miklos Szeredi <mszeredi@redhat.com>
> > Date:   Fri Jul 29 12:05:24 2016 +0200
> > 
> >     ovl: share inode for hard link
> 
> That's rather complex, but the principle is simple: use the inode hash
> for all upper inodes that may have aliases.  Aliasable means the
> underlying inode isn't a directory and has i_nlink > 1, so all I have
> to do is perform a lookup through the hash if the underlying is
> aliasable, invalidate the dentry in d_revalidate if the aliasing
> conditions to the underlying change and manually handle hard links and
> it should all work.
> 
> Like this?

Sounds reasonable to me. I did basic testing and this seems to work for me.

In general, I am having random crashes. I just get following on serial
console

------[Cut Here]----------

And nothing after that.

Still trying to narrow down.

Vivek

Thread

Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Vivek Goyal <vgoyal@redhat.com> - 2017-02-15 21:40 +0100
  Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-16 17:00 +0100
    Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Al Viro <viro@ZenIV.linux.org.uk> - 2017-02-17 04:00 +0100
      Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-17 18:40 +0100
        Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Vivek Goyal <vgoyal@redhat.com> - 2017-02-17 21:50 +0100
          Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-19 04:30 +0100
            Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount Vivek Goyal <vgoyal@redhat.com> - 2017-02-20 20:30 +0100
              Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-21 01:40 +0100

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