Re: [PATCH] xfs: remove experimental tag for reflinks

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Thu, Aug 31, 2017 at 10:55:31AM -0500, Eric Sandeen wrote:
> On 8/31/17 10:31 AM, Darrick J. Wong wrote:
> > On Thu, Aug 31, 2017 at 03:30:19PM +0200, Christoph Hellwig wrote:
> >> On Thu, Aug 31, 2017 at 08:43:21AM -0400, Brian Foster wrote:
> >>> FWIW, I don't really have a strong opinion. To me, removing experimental
> >>> means we feel the code has stabilized long enough in principle, there
> >>> are no significant problems (i.e., corruption/crash vectors) that we are
> >>> aware of and the feature is complete (full userspace tool support, etc).
> >>> The in-core extent list thing seems like more of a general problem to me
> >>
> >> Agreed so far.
> > 
> > <nod> Dave?  Eric?  Any perspective you'd like to offer? :)
> 
> This is a bit of a naiive question, but how many applications are out
> there that can be used with reflink right now?  This would obviously

Anything that uses cp --reflink, which could be any number of deploy
scripts to VM "snapshot" tools.  ISTR that cifs & nfs now both support
reflink too, and now that ocfs2 also supports the ficlone* ioctls (sort
of) we can expect wider use.

dupremove (offline dedupe tool for btrfs) can also talk to xfs/ocfs2.

> delay things a bit, but I had considered writing something up for
> LWN or Fedora Planet or $WHATEVER describing these new xfs features,
> how they can be used, and encourage some early-adopter testing.  Try
> to get some buzz going and some real-world use.

I know there's already some dedicated experimenters using reflink...

> It's always a catch 22; nobody uses it until it's marked stable,
> but we never know if it's really stable until people outside the
> development community use it.  ;)
> 
> As for the allocation issues w/ the in core extent list, yeah, that
> worries me.

Yeah.  On the one hand it's a pre-existing condition that's orthogonal
to reflink (and hey, we even put in cowextsize to mitigate the problems
on VMs) but OTOH it probably gets worse with cow.

--D

> 
> -Eric
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