Re: [Qemu-devel] [PATCH 1/2] qcow2: Make size_to_clusters() return int64_t

[Eric Blake <eblake@redhat.com>]

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On 09/08/2015 02:09 PM, Max Reitz wrote:
> Sadly, some images may have more clusters than what can be represented
> using a plain int. We should be prepared for that case (in
> qcow2_check_refcounts() we actually were trying to catch that case, but
> since size_to_clusters() truncated the returned value, that check never
> did anything useful).
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/qcow2-cluster.c | 20 +++++++++++---------
>  block/qcow2.h         |  2 +-
>  2 files changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
> index 2975b83..a34f0b1 100644
> --- a/block/qcow2-cluster.c
> +++ b/block/qcow2-cluster.c
> @@ -473,8 +473,8 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
>      unsigned int l2_index;
>      uint64_t l1_index, l2_offset, *l2_table;
>      int l1_bits, c;
> -    unsigned int index_in_cluster, nb_clusters;
> -    uint64_t nb_available, nb_needed;
> +    unsigned int index_in_cluster;
> +    uint64_t nb_available, nb_needed, nb_clusters;

Most uses are storing the results unsigned...

>  
> -static inline int size_to_clusters(BDRVQcow2State *s, int64_t size)
> +static inline int64_t size_to_clusters(BDRVQcow2State *s, int64_t size)
>  {
>      return (size + (s->cluster_size - 1)) >> s->cluster_bits;
>  }

...and the function itself doesn't appear to intentionally return
negative (unless size was passed in as negative, but then that may be
accidental).  Should it just return uint64_t instead?

At any rate, I agree that 'int' is too small, so:
Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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