From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:45224)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <kwolf@redhat.com>) id 1Uzlf8-0004w9-60
	for qemu-devel@nongnu.org; Thu, 18 Jul 2013 06:42:19 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <kwolf@redhat.com>) id 1Uzlf7-00070F-8y
	for qemu-devel@nongnu.org; Thu, 18 Jul 2013 06:42:18 -0400
Received: from mx1.redhat.com ([209.132.183.28]:36941)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <kwolf@redhat.com>) id 1Uzlf7-00070B-1E
	for qemu-devel@nongnu.org; Thu, 18 Jul 2013 06:42:17 -0400
Date: Thu, 18 Jul 2013 12:42:09 +0200
From: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20130718104209.GH3582@dhcp-200-207.str.redhat.com>
References: <51E66ACD.70706@redhat.com>
	<20130717102551.GF2458@dhcp-200-207.str.redhat.com>
	<CAN05THSiKdxONhHboG5a43KSeAZGnpq9=-T1YAKNipPQccDjww@mail.gmail.com>
	<51E6C5FC.1030304@redhat.com>
	<CAN05THSiLVt-cWq8x26Z6kdsAw0tvGf6zMDeJD8tVmZ=jCTSQQ@mail.gmail.com>
	<7C1EEB41-E2B3-4186-9188-379F02E76FF9@kamp.de>
	<51E6CE81.6000400@redhat.com>
	<36C25446-54C7-4D1F-9D8D-E8A3991489BD@kamp.de>
	<20130718092316.GG3582@dhcp-200-207.str.redhat.com>
	<51E7C260.50404@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <51E7C260.50404@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target
	on convert
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>, Peter Lieven <pl@kamp.de>, qemu-devel <qemu-devel@nongnu.org>, ronnie sahlberg <ronniesahlberg@gmail.com>

Am 18.07.2013 um 12:24 hat Paolo Bonzini geschrieben:
> Il 18/07/2013 11:23, Kevin Wolf ha scritto:
> > Am 17.07.2013 um 19:48 hat Peter Lieven geschrieben:
> >>
> >> Am 17.07.2013 um 19:04 schrieb Paolo Bonzini <pbonzini@redhat.com>:
> >>
> >>> Il 17/07/2013 19:02, Peter Lieven ha scritto:
> >>>> For Disks we always use read/write16 so i think we Should also use writesame16. Or not?
> >>>
> >>> Yes.
> >>>
> >>> Remember you can still use UNMAP if LBPRZ=0.
> >>
> >> I can always use it if writesame is not available, but in this case bdi->discard_zeroes must be 0.
> >>
> >> Maybe we should call it discard_writes_zeroes or similar.
> >>
> >> Discard_zeroes is sth that should only indicate if lbprz == 1. At least if we refer to the Linux ioctl. We could include both in BDI.
> > 
> > Maybe what we really should do is to define different operations (with
> > an exact behaviour) instead of having one bdrv_discard() and then adding
> > flags everywhere to tell what the operation is doing exactly.
> 
> A BDRV_MAY_UNMAP flag for bdrv_write_zeroes?

Something like that, yes.

Kevin