Re: cross-subvolume cp --reflink

[Marc MERLIN <marc@merlins.org>]

On Sun, Aug 19, 2012 at 12:08:01AM -0500, Mitch Harder wrote:
> On Fri, Aug 17, 2012 at 12:20 AM, Marc MERLIN <marc@merlins.org> wrote:
> > On Thu, Aug 16, 2012 at 09:20:00PM -0700, james northrup wrote:
> >> dunno if this thread is dead, but im inclined to patch in cp --reflink
> >> to "fdupes" prog.  It  currently does provide a poor-man's dedupe via
> >> md5sum and hardlink, or delete.
> >>
> >> all the better if the distro-kernels can backport cross-snapshot
> >> reflinks sooner than later.
> >
> > So, I'd love for cp --reflink to bring back a deleted VM (huge file) from a
> > snapshot back to trunk without duplicating it.
> > But how would fdupes help? I can't hardlink between two snapshots, can I?
> >
> > gandalfthegreat:/mnt/btrfs_pool1# ln usr_weekly_20120812_00\:02\:01/svn-commit.tmp  usr/test
> > ln: failed to create hard link `usr/test' => `usr_weekly_20120812_00:02:01/svn-commit.tmp': Invalid cross-device link
> >
> > So, is there anything user space can do without kernel support?
> >
> 
> A cross-subvolume copy patch has made it into 3.6_rc
> 
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=362a20c5e27614739c4
> 
> This patch will allow cp --reflink across subvolumes, as long as the
> copy does not cross mount points.

I missed that, that's great news, thanks to all those involved in getting
this in.

Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/