Re: [Qemu-devel] [PATCH 14/20] qcow2: Factor out count_cow_clusters

[Kevin Wolf]

Am 19.04.2012 23:18, schrieb Marcelo Tosatti:
> On Thu, Apr 19, 2012 at 05:14:20PM -0300, Marcelo Tosatti wrote:
>>> There is one intended change in functionality in this patch, which is
>>> that it allocates new clusters even when it could satisfy the first part
>>> of the request with already allocated clusters. In order to check if
>>> there is a problem with this scenario, the following patch should revert
>>> to the old behaviour:
>>>
>>> --- a/block/qcow2-cluster.c
>>> +++ b/block/qcow2-cluster.c
>>> @@ -847,7 +847,7 @@ again:
>>>          keep_clusters = count_contiguous_clusters(nb_clusters,
>>> s->cluster_size,
>>>                                                    &l2_table[l2_index],
>>> 0, 0);
>>>          assert(keep_clusters <= nb_clusters);
>>> -        nb_clusters -= keep_clusters;
>>> +        nb_clusters = 0;
>>>      } else {
>>>          /* For the moment, overwrite compressed clusters one by one */
>>>          if (cluster_offset & QCOW_OFLAG_COMPRESSED) {
>>>
>>> The rest is meant to be a functionally equivalent rewrite of the old
>>> code that was required in order to allow this change.
>>
>> Testing.
> 
> Corruption gone with patch above.

Okay, so something must be wrong only with the new code paths, which
makes things a bit easier. I'll have another closer look. Stefan, can
you re-review 250196f1 as well?

Kevin