Odd BTRFS COW behaviour

James Hogarth james.hogarth at gmail.com
Fri Jan 17 14:10:10 UTC 2014

On 17 January 2014 13:38, Chris Murphy <lists at colorremedies.com> wrote:

> On Jan 17, 2014, at 6:06 AM, James Hogarth <james.hogarth at gmail.com>
> wrote:
> So far as I understand it when in the same pool cross-subvolume COW should
> be valid (as shown in /data on the server) - even if technically under
> separate mounts.
> I haven't yet found anything newer than this:
> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=362a20c5e27614739c4
> The clone can be in different subvolumes but the source and destination
> must be the same mount point.
> There's a similar effect with btrfs send that might be related, and it has
> patches upstream.
> http://www.spinics.net/lists/linux-btrfs/msg30852.html

Thanks that commit does indeed match my behaviour ... even if it seems a
bit messed up all things considered ...

I might use a Fedora Live instance and remove the /home mount point whilst
maintaining as a subvolume within root ...

In fact given this behaviour I'm thinking that a bug against anaconda might
be warranted to  make home a subvolume (for easy snapshotting etc) but to
not explicitly mount it to get the maximum flexibility...

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