From mboxrd@z Thu Jan  1 00:00:00 1970
From: "J. Bruce Fields" <bfields@redhat.com>
Subject: Re: What to do about subvolumes?
Date: Tue, 7 Dec 2010 15:45:48 -0500
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Cc: Chris Mason <chris.mason@oracle.com>,
	Dave Chinner <david@fromorbit.com>,
	Josef Bacik <josef@redhat.com>,
	linux-btrfs <linux-btrfs@vger.kernel.org>,
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	ssorce <ssorce@redhat.com>
To: hch <hch@lst.de>
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On Tue, Dec 07, 2010 at 05:52:13PM +0100, hch wrote:
> On Fri, Dec 03, 2010 at 05:45:26PM -0500, J. Bruce Fields wrote:
> > We're using statfs64.fs_fsid for this; I believe that's both stable
> > across reboots and distinguishes between subvolumes, so that's OK.
> 
> It's a field that doesn't have any useful specification and basically
> contains random garbage that a filesystem put into it.  Using it is a
> very bad idea.

I meant the above statement to apply only to btrfs; and nfs-utils is
using fs_fsid only in the case where the filesystem type is "btrfs".  So
I believe the current code does work.

But I agree that constructing filehandles differently based on a
strcmp() of the filesystem type is not a sustainable design, to say the
least.

--b.