[RFC] allow enabling reflinks at runtime

[Dave Chinner]

On Thu, Jun 02, 2016 at 04:19:07PM +0200, Christoph Hellwig wrote:
> I've had some vocal user requests to allow enabling reflinks at run time,
> which happens to be a mostly trivial feature.  The only caveat is that we
> need a large enough log size to support the reflink requirements, but for
> typical large file systems that's not an issue.

Hmmm - how does this interact with all the rmap code? I was not
planning on enabling reflink without rmap and vice versa simply
because it makes the validation and testing matrix vastly more
complex. Indeed, having reflink turned on after a filesystem has
aged for some time (i.e. from unknown initial conditions) makes
validation especially tricky....

Darrick?

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com