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

[Eric Blake <eblake@redhat.com>]

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