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From: "Pavel Dovgalyuk" <dovgaluk@ispras.ru>
References: <20160920123126.5400.29283.stgit@PASHA-ISP.def.inno>
	<20160920123138.5400.67174.stgit@PASHA-ISP.def.inno>
	<8ebdaf52-f7f9-c6ac-3a85-3149b2e55346@redhat.com>
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Date: Tue, 20 Sep 2016 15:43:11 +0300
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Subject: Re: [Qemu-devel] [PATCH v3 2/8] block: set snapshot option for
 block devices in blkreplay module
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To: 'Paolo Bonzini' <pbonzini@redhat.com>, 'Pavel Dovgalyuk' <pavel.dovgaluk@ispras.ru>, qemu-devel@nongnu.org
Cc: peter.maydell@linaro.org, jasowang@redhat.com, quintela@redhat.com, mst@redhat.com

> From: Paolo Bonzini [mailto:pbonzini@redhat.com]
> On 20/09/2016 14:31, Pavel Dovgalyuk wrote:
> >      /* Open the image file */
> >      bs->file = bdrv_open_child(NULL, options, "image",
> > @@ -40,6 +112,43 @@ static int blkreplay_open(BlockDriverState *bs, QDict *options, int
> flags,
> >          goto fail;
> >      }
> >
> > +    opts = qemu_opts_create(&blkreplay_runtime_opts, NULL, 0, &error_abort);
> > +    qemu_opts_absorb_qdict(opts, options, &local_err);
> > +    if (local_err) {
> > +        ret = -EINVAL;
> > +        goto fail;
> > +    }
> > +
> > +    /* Prepare options QDict for the overlay file */
> > +    qdict_put(snapshot_options, "file.driver",
> > +              qstring_from_str("file"));
> > +    qdict_put(snapshot_options, "driver",
> > +              qstring_from_str("qcow2"));
> > +
> > +    snapshot = qemu_opt_get(opts, "overlay");
> > +    if (snapshot) {
> > +        qdict_put(snapshot_options, "file.filename",
> > +                  qstring_from_str(snapshot));
> > +    } else {
> > +        char tmp_filename[PATH_MAX + 1];
> > +        ret = get_tmp_filename(tmp_filename, PATH_MAX + 1);
> > +        if (ret < 0) {
> > +            error_setg_errno(errp, -ret, "Could not get temporary filename");
> > +            goto fail;
> > +        }
> 
> No, this is unnecessary.  The image is unused in this case, so you can
> specify the overlay as image=foo.qcow2.

This branch allows user do not bother about overlays at all.
Driver will automatically create temporary snapshot.

Pavel Dovgalyuk