Re: What to do about subvolumes?

[Chris Mason <chris.mason@oracle.com>]

Excerpts from C Anthony Risinger's message of 2010-12-01 11:03:23 -0500:
> On Wed, Dec 1, 2010 at 10:01 AM, Chris Mason <chris.mason@oracle.com> wrote:
> > Excerpts from C Anthony Risinger's message of 2010-12-01 09:51:55 -0500:
> >> On Wed, Dec 1, 2010 at 8:21 AM, Josef Bacik <josef@redhat.com> wrote:
> >> >
> >> > === How do we want subvolumes to work from a user perspective? ===
> >> >
> >> > 1) Users need to be able to create their own subvolumes.  The permission
> >> > semantics will be absolutely the same as creating directories, so I don't think
> >> > this is too tricky.  We want this because you can only take snapshots of
> >> > subvolumes, and so it is important that users be able to create their own
> >> > discrete snapshottable targets.
> >> >
> >> > 2) Users need to be able to snapshot their subvolumes.  This is basically the
> >> > same as #1, but it bears repeating.
> >>
> >> could it be possible to convert a directory into a volume?  or at
> >> least base a snapshot off it?
> >
> > I'm afraid this turns into the same complexity as creating a new volume
> > and copying all the files/dirs in by hand.
> 
> ok; if i create an empty volume, and use cp --reflink, it would have
> the desired affect though, right?

Almost, for no good reason at all our cp --reflink doesn't reflink
across subvols.  I'll get that fixed up.

-chris
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