From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:56909)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <Pavel.Dovgaluk@ispras.ru>) id 1aTrfv-0004ui-Sc
	for qemu-devel@nongnu.org; Thu, 11 Feb 2016 08:52:52 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <Pavel.Dovgaluk@ispras.ru>) id 1aTrfs-0006jc-L2
	for qemu-devel@nongnu.org; Thu, 11 Feb 2016 08:52:51 -0500
Received: from mail.ispras.ru ([83.149.199.45]:36829)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <Pavel.Dovgaluk@ispras.ru>) id 1aTrfs-0006jA-EB
	for qemu-devel@nongnu.org; Thu, 11 Feb 2016 08:52:48 -0500
From: "Pavel Dovgalyuk" <Pavel.Dovgaluk@ispras.ru>
References: <20160210091259.10024.74767.stgit@PASHA-ISP>
	<20160210091323.10024.5684.stgit@PASHA-ISP>
	<20160211095605.GB4647@stefanha-x1.localdomain>
In-Reply-To: <20160211095605.GB4647@stefanha-x1.localdomain>
Date: Thu, 11 Feb 2016 16:52:42 +0300
Message-ID: <002c01d164d3$7a8b4680$6fa1d380$@Dovgaluk@ispras.ru>
MIME-Version: 1.0
Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: 7bit
Content-Language: ru
Subject: Re: [Qemu-devel] [PATCH v2 4/4] replay: introduce block devices
	record/replay
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: 'Stefan Hajnoczi' <stefanha@redhat.com>
Cc: edgar.iglesias@xilinx.com, peter.maydell@linaro.org, igor.rubinov@gmail.com, mark.burton@greensocs.com, real@ispras.ru, hines@cert.org, qemu-devel@nongnu.org, maria.klimushenkova@ispras.ru, kwolf@redhat.com, pbonzini@redhat.com, batuzovk@ispras.ru, alex.bennee@linaro.org, fred.konrad@greensocs.com

> From: Stefan Hajnoczi [mailto:stefanha@redhat.com]
> On Wed, Feb 10, 2016 at 12:13:23PM +0300, Pavel Dovgalyuk wrote:
> > @@ -784,7 +798,11 @@ BlockAIOCB *blk_aio_flush(BlockBackend *blk,
> >          return blk_abort_aio_request(blk, cb, opaque, -ENOMEDIUM);
> >      }
> >
> > -    return bdrv_aio_flush(blk->bs, cb, opaque);
> > +    if (replay_mode == REPLAY_MODE_NONE) {
> > +        return bdrv_aio_flush(blk->bs, cb, opaque);
> > +    } else {
> > +        return replay_aio_flush(blk->bs, cb, opaque);
> > +    }
> >  }
> 
> I am only looking at this patch in isolation and am not familiar with
> the record/replay work, but these changes appear invasive.  In order for
> record/replay to keep working in the future, everyone touching block
> layer code must be familiar with the principles of how record/replay
> works.  This patch does not include documentation.

We've already discussed it with Kevin.
He proposes adding new block driver for record/replay.

> Can you point me to documentation that explains the how record replay
> works?

There is some information about it in docs/replay.txt and in
http://wiki.qemu.org/Features/record-replay

Pavel Dovgalyuk