Here refcount of cluster at @cluster_offset reached 0, so we "free"
that cluster. Not a cluster at @offset. The thing that save us from the
bug is that L2 tables and refblocks are discarded one by one. Still,
let's be precise.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
---
 block/qcow2-refcount.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 8e649b008e..543fcf289c 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -887,14 +887,15 @@ static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs,
             void *table;
 
             table = qcow2_cache_is_table_offset(s->refcount_block_cache,
-                                                offset);
+                                                cluster_offset);
             if (table != NULL) {
                 qcow2_cache_put(s->refcount_block_cache, &refcount_block);
                 old_table_index = -1;
                 qcow2_cache_discard(s->refcount_block_cache, table);
             }
 
-            table = qcow2_cache_is_table_offset(s->l2_table_cache, offset);
+            table = qcow2_cache_is_table_offset(s->l2_table_cache,
+                                                cluster_offset);
             if (table != NULL) {
                 qcow2_cache_discard(s->l2_table_cache, table);
             }
-- 
2.29.2