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Re: [Qemu-devel] [PATCH v2 2/3] docs/qcow2: Correct refcount_block_entri
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH v2 2/3] docs/qcow2: Correct refcount_block_entries |
Date: |
Tue, 02 Sep 2014 16:28:53 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.7.0 |
On 09/02/2014 04:25 PM, 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
> accordingly.
>
> Signed-off-by: Max Reitz <address@hidden>
> ---
> docs/specs/qcow2.txt | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
Reviewed-by: Eric Blake <address@hidden>
>
> diff --git a/docs/specs/qcow2.txt b/docs/specs/qcow2.txt
> index cfbc8b0..0a878aa 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:
>
> - refcount_block_entries = (cluster_size / sizeof(uint16_t))
> + refcount_block_entries = (cluster_size * 8 / refcount_bits)
>
> refcount_block_index = (offset / cluster_size) % refcount_block_entries
> refcount_table_index = (offset / cluster_size) / refcount_block_entries
>
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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