Date: Sat, 19 Sep 2009 14:14:30 +0900
To: jens.axboe@oracle.com
Cc: neilb@suse.de, hch@infradead.org, James.Bottomley@suse.de,
       lars.ellenberg@linbit.com, linux-kernel@vger.kernel.org,
       drbd-dev@lists.linbit.com, akpm@linux-foundation.org,
       bart.vanassche@gmail.com, davej@redhat.com, gregkh@suse.de,
       kosaki.motohiro@jp.fujitsu.com, kyle@moffetthome.net, lmb@suse.de,
       torvalds@linux-foundation.org, nab@linux-iscsi.org, knikanth@suse.de,
       philipp.reisner@linbit.com, sam@ravnborg.org
Subject: Re: [GIT PULL] DRBD for 2.6.32
From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
In-Reply-To: <20090918200803.GM23126@kernel.dk>
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	<19122.65335.126937.476968@notabene.brown>
	<20090918200803.GM23126@kernel.dk>
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On Fri, 18 Sep 2009 22:08:03 +0200
Jens Axboe <jens.axboe@oracle.com> wrote:

> On Fri, Sep 18 2009, Neil Brown wrote:
> > On Thursday September 17, hch@infradead.org wrote:
> > > On Thu, Sep 17, 2009 at 10:02:45AM -0600, James Bottomley wrote:
> > > > So I think Christoph's NAK is rooted in the fact that we have a
> > > > proliferation of in-kernel RAID implementations and he's trying to
> > > > reunify them all again.
> > > > 
> > > > As part of the review, reusing the kernel RAID (and actually logging)
> > > > logic did come up and you added it to your todo list.  Perhaps expanding
> > > > on the status of that would help, since what's being looked for is that
> > > > you're not adding more work to the RAID reunification effort and that
> > > > you do have a plan and preferably a time frame for coming into sync with
> > > > it.
> > > 
> > > Yes.  RDBD has spend tons of time out of tree, and if they want to put
> > > it in now I think requiring them to do their homework is a good idea.
> > 
> > What homework?
> > 
> > If there was a sensible unifying framework in the kernel that they
> > could plug in to, then requiring them do to that might make sense.  But
> > there isn't.  You/I/We haven't created a solution (i.e. there is no
> > equivalent of the VFS for virtual block devices) and saying that
> > because we haven't they cannot merge DRBD hardly seems fair.
> > 
> > Indeed, merging DRBD must be seen as a *good* thing as we then have
> > more examples of differing requirements against which a proposed
> > solution can be measured and tested.
> > 
> > I thought the current attitude was "merge then fix".  That is what the
> > drivers/staging tree seems to be all about.  Maybe you could argue
> > that DRBD should go in to 'staging' first (though I don't think that
> > is appropriate or require myself), but keeping it out just seems
> > wrong.
> 
> FWIW, I agree with Neil here. If drbd is merge clean, lets go ahead and
> merge it. While it would be nice to offload the raid unification onto
> drbd, it's not exactly fair.

I guess that Christoph is worry about adding another user interface
for kinda device management; once we merge this, we can't fix it (for
the raid unification).

BTW, DM already has something like drbd? I thought that there is a
talk about that new target at LinuxCon.
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