Re: [Qemu-devel] [PATCH v2 4/4] replay: introduce block devices record/replay

[Pavel Dovgalyuk]

> From: Stefan Hajnoczi [mailto:address@hidden
> 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