On 28.06.20 13:02, Alberto Garcia wrote:
> qcow2_get_cluster_offset() takes an (unaligned) guest offset and
> returns the (aligned) offset of the corresponding cluster in the qcow2
> image.
> 
> In practice none of the callers need to know where the cluster starts
> so this patch makes the function calculate and return the final host
> offset directly. The function is also renamed accordingly.
> 
> There is a pre-existing exception with compressed clusters: in this
> case the function returns the complete cluster descriptor (containing
> the offset and size of the compressed data). This does not change with
> this patch but it is now documented.
> 
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  block/qcow2.h         |  4 ++--
>  block/qcow2-cluster.c | 42 +++++++++++++++++++++++-------------------
>  block/qcow2.c         | 24 +++++++-----------------
>  3 files changed, 32 insertions(+), 38 deletions(-)

[...]

> diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
> index 4b5fc8c4a7..9ab41cb728 100644
> --- a/block/qcow2-cluster.c
> +++ b/block/qcow2-cluster.c

[...]

> @@ -537,8 +542,6 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
>          bytes_needed = bytes_available;
>      }
>  
> -    *cluster_offset = 0;
> -

You drop this line without replacement now.  That means that
*host_offset is no longer set to 0 if the L1 entry is out of bounds or
empty (which causes this function to return QCOW2_CLUSTER_UNALLOCATED
and no error).  Was that intentional?

Max