[libvirt PATCH v2 2/2] storage_file: add support to probe cluster_size from QCOW2 images

[Pavel Hrdina]

On Fri, May 21, 2021 at 09:40:21AM +0200, Peter Krempa wrote:
> On Thu, May 20, 2021 at 17:14:32 +0200, Pavel Hrdina wrote:
> > >From QEMU docs/interop/qcow2.txt :
> > 
> >    Byte  20 - 23:   cluster_bits
> >                     Number of bits that are used for addressing an offset
> >                     within a cluster (1 << cluster_bits is the cluster size).
> > 
> > With this patch libvirt will be able to report the current cluster_size
> > for all existing storage volumes managed by storage driver.
> > 
> > Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
> > ---
> > 
> > Changes in v2:
> >     - Reworkded to use callback.
> > 
> >  src/storage/storage_util.c            |  3 ++
> >  src/storage_file/storage_file_probe.c | 70 ++++++++++++++++++++-------
> >  2 files changed, 56 insertions(+), 17 deletions(-)
> 
> [...]
> 
> > @@ -468,6 +477,28 @@ qcow2GetExtensions(const char *buf,
> >  }
> >  
> >  
> > +static unsigned long long
> > +qcow2GetClusterSize(const char *buf,
> > +                    size_t buf_size,
> > +                    int endian)
> 
> The 'endian' argument makes sense only for generic getters. You know
> that qcow2 has always LV_BIG_ENDIAN set.
> 
> > +{
> > +    int clusterBits = 0;
> > +
> > +    if ((QCOWX_HDR_CLUSTER_BITS_OFFSET + 4) > buf_size)
> > +        return 0;
> > +
> > +    if (endian == LV_LITTLE_ENDIAN)
> > +        clusterBits = virReadBufInt32LE(buf + QCOWX_HDR_CLUSTER_BITS_OFFSET);
> > +    else
> > +        clusterBits = virReadBufInt32BE(buf + QCOWX_HDR_CLUSTER_BITS_OFFSET);
> > +
> > +    if (clusterBits > 0)
> > +        return 1 << clusterBits;
> > +
> > +    return 0;
> > +}
> 
> Drop the 'endian' argument with appropriate cleanup and:
> 
> Reviewed-by: Peter Krempa <pkrempa at redhat.com>

Fixed and pushed. Thanks for the review.

Pavel
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