Re: [Qemu-block] [Qemu-devel] [PATCH] qcow2: Reset free_cluster_index when allocating a new refcount block

[Eric Blake]

On 03/21/2018 08:30 AM, Eric Blake wrote:
> On 03/20/2018 08:55 AM, Alberto Garcia wrote:

> > This can be reproduced easily:
> >
> >       qemu-img create -f qcow2 -o cluster_size=512 hd.qcow2 1M
> >       qemu-io -c 'write 0 124k' hd.qcow2
>
> This reproduction fails if you use non-default refcount_order...
>
> > +++ b/tests/qemu-iotests/121
> > @@ -93,6 +93,26 @@ $QEMU_IO -c 'write 63M 130K' "$TEST_IMG" | 
> > _filter_qemu_io
> >   _check_test_img
> > +echo
> > +echo '=== Allocating a new refcount block must not leave holes in the 
> > image ==='
> > +echo
> > +
> > +IMGOPTS='cluster_size=512' _make_test_img 1M
>
> ...so here, I think IMGOPTS also has to include refcount_bits=4, so that 
> calling iotests './check -o refcount_bits=3' or similar doesn't fail the 
> test.

Except that it's spelled refcount_bits=16 vs. refcount_bits=8 (we 
convert refcount_bits as a power of 2 to refcount_order as an exponent 
value written into the qcow2 header).

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org