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Message-Id: <20090922072617U.fujita.tomonori@lab.ntt.co.jp>
Date: Tue, 22 Sep 2009 07:27:21 +0900
From: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To: lars.ellenberg@...bit.com
Cc: arjan@...radead.org, fujita.tomonori@....ntt.co.jp, lmb@...e.de,
jens.axboe@...cle.com, neilb@...e.de, hch@...radead.org,
James.Bottomley@...e.de, linux-kernel@...r.kernel.org,
drbd-dev@...ts.linbit.com, akpm@...ux-foundation.org,
bart.vanassche@...il.com, davej@...hat.com, gregkh@...e.de,
kosaki.motohiro@...fujitsu.com, kyle@...fetthome.net,
torvalds@...ux-foundation.org, nab@...ux-iscsi.org,
knikanth@...e.de, philipp.reisner@...bit.com, sam@...nborg.org,
Mauelshagen@...hat.com
Subject: Re: [GIT PULL] DRBD for 2.6.32
On Mon, 21 Sep 2009 18:53:21 +0200
Lars Ellenberg <lars.ellenberg@...bit.com> wrote:
> On Mon, Sep 21, 2009 at 04:52:52PM +0200, Arjan van de Ven wrote:
> > On Mon, 21 Sep 2009 16:43:08 +0200
> > Lars Ellenberg <lars.ellenberg@...bit.com> wrote:
> > > We can choose whatever user-kernel interface you like,
> > > and change it with every dot release --
> > > we'd just need to add additional compat code into
> > > the drbdsetup userland binary.
> >
> > uh no.
> >
> > the kernel<->userspace ABI is stable.
> > we don't go about randomly changing it
> > (extending it is fine obviously)
>
> That's not what I meant, of course that is and needs to be stable.
> Sorry, I exagerated to make a point.
>
> Point was:
> mdadm configured md.
> dmsetup configured dm.
> drbdsetup configure drbd.
>
> If and when "something" is done to "unify" things on the implementation
> level, it is likely to also unify the "kernel<->userspace" configuration
> interface.
>
> If it happens, once that happens, that _will_ be an ABI break.
You misunderstand the raid unification.
We will not unify the kernel<->userspace configuration interface
because we can't break the kernel<->userspace ABI.
We plan to unify the multiple device frameworks, but the unified
framework must support the all existing ABIs.
So adding another 'drbd' ABI hurts us.
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