On 04.11.19 16:04, Max Reitz wrote:
> On 26.10.19 23:25, Alberto Garcia wrote:
>> Setting the QCOW_OFLAG_ZERO bit of the L2 entry is forbidden if an
>> image has subclusters. Instead, the individual 'all zeroes' bits must
>> be used.
>>
>> Signed-off-by: Alberto Garcia <be...@igalia.com>
>> ---
>> block/qcow2-cluster.c | 14 ++++++++++----
>> 1 file changed, 10 insertions(+), 4 deletions(-)
>>
>> diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
>> index e67559152f..3e4ba8d448 100644
>> --- a/block/qcow2-cluster.c
>> +++ b/block/qcow2-cluster.c
>> @@ -1852,7 +1852,7 @@ static int zero_in_l2_slice(BlockDriverState *bs,
>> uint64_t offset,
>> assert(nb_clusters <= INT_MAX);
>>
>> for (i = 0; i < nb_clusters; i++) {
>> - uint64_t old_offset;
>> + uint64_t old_offset, l2_entry = 0;
>> QCow2ClusterType cluster_type;
>>
>> old_offset = get_l2_entry(s, l2_slice, l2_index + i);
>> @@ -1869,12 +1869,18 @@ static int zero_in_l2_slice(BlockDriverState *bs,
>> uint64_t offset,
>>
>> qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice);
>> if (cluster_type == QCOW2_CLUSTER_COMPRESSED || unmap) {
>> - set_l2_entry(s, l2_slice, l2_index + i, QCOW_OFLAG_ZERO);
>> qcow2_free_any_clusters(bs, old_offset, 1,
>> QCOW2_DISCARD_REQUEST);
>
> It feels wrong to me to free the cluster before updating the L2 entry.(Although it’s pre-existing, as set_l2_entry() is just an in-cache operation anyway :-/) Max
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