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Date: Mon, 1 Sep 2014 12:55:07 +0200
From: =?iso-8859-1?Q?Beno=EEt?= Canet <benoit.canet@irqsave.net>
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Subject: Re: [Qemu-devel] [PATCH 2/2] docs/qcow2: Correct
 refcount_block_entries
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To: Max Reitz <mreitz@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>

The Friday 29 Aug 2014 =E0 23:45:27 (+0200), Max Reitz wrote :
> A refblock entry may have a different size than 16 bits, it may even be
> smaller than a byte. Correct the refcount_block_entries calculation

Now if the refblock entry size is smaller than a byte

> accordingly.
>=20
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  docs/specs/qcow2.txt | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>=20
> diff --git a/docs/specs/qcow2.txt b/docs/specs/qcow2.txt
> index cfbc8b0..531c478 100644
> --- a/docs/specs/qcow2.txt
> +++ b/docs/specs/qcow2.txt
> @@ -183,7 +183,7 @@ blocks and are exactly one cluster in size.
>  Given a offset into the image file, the refcount of its cluster can be=
 obtained
>  as follows:
> =20
> -    refcount_block_entries =3D (cluster_size / sizeof(uint16_t))
> +    refcount_block_entries =3D (cluster_size / (refcount_bits / 8))

This give a divide by zero error.                   ^

> =20
>      refcount_block_index =3D (offset / cluster_size) % refcount_block_=
entries
>      refcount_table_index =3D (offset / cluster_size) / refcount_block_=
entries
> --=20
> 2.1.0
>=20
>=20