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Date: Wed, 19 Nov 2014 01:59:08 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Andy Whitcroft <apw@canonical.com>, Serge Hallyn <serge.hallyn@ubuntu.com>,
        Neil Brown <neilb@suse.de>, linux-unionfs@vger.kernel.org,
        Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: How to cope with two incompatible overlayfs formats out in the
 wild
Message-ID: <20141119015908.GV7996@ZenIV.linux.org.uk>
References: <CAJfpegtG68g=dDi7j-WfhkuJidZRBg46vyuWg8CTrW3TrW_nYw@mail.gmail.com>
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On Tue, Nov 18, 2014 at 03:28:03PM +0100, Miklos Szeredi wrote:

> So from mainline we need two things:
> 
>   - when mounting distinguish between old and new format.
> 
>   - userspace can detect which formats are supported by the kernel.
> 
> If we'd have a different filesystem type for the old and new formats,
> then that would solve both (checking /proc/filesystems would indicate
> which one is supported).
> 
> Unfortunately that would mean having to change "overlayfs" type to
> something else in 3.18.  Question is, is there some sane name which
> would fit?  "overlayfs2" is perhaps the best, but I'm not overly
> enthusiastic about it.
> 
> Any other ideas?

Umm...  What does the old one do when it sees workdir=<something> in the
options?
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