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References: <20160921113303.1420.63544.stgit@PASHA-ISP.def.inno>
	<20160921113320.1420.80132.stgit@PASHA-ISP.def.inno>
From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Wed, 21 Sep 2016 17:37:01 +0200
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Subject: Re: [Qemu-devel] [PATCH v4 3/8] block: don't make snapshots for
 filters
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To: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>, qemu-devel@nongnu.org
Cc: peter.maydell@linaro.org, jasowang@redhat.com, quintela@redhat.com, mst@redhat.com



On 21/09/2016 13:33, Pavel Dovgalyuk wrote:
> This patch disables snapshotting for block driver filters.
> It is needed, because snapshots should be created
> in underlying disk images, not in filters itself.

I don't understand this patch.  Who would take care of doing the
bdrv_snapshot_goto on the underlying image?

Paolo

> Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
> ---
>  block/snapshot.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/block/snapshot.c b/block/snapshot.c
> index bf5c2ca..8998b8b 100644
> --- a/block/snapshot.c
> +++ b/block/snapshot.c
> @@ -184,6 +184,9 @@ int bdrv_snapshot_goto(BlockDriverState *bs,
>      if (!drv) {
>          return -ENOMEDIUM;
>      }
> +    if (drv->is_filter) {
> +        return 0;
> +    }
>      if (drv->bdrv_snapshot_goto) {
>          return drv->bdrv_snapshot_goto(bs, snapshot_id);
>      }
>