@@ -521,7 +521,15 @@ static inline QCow2ClusterType qcow2_get_cluster_type(BlockDriverState *bs,
}
return QCOW2_CLUSTER_ZERO_PLAIN;
} else if (!(l2_entry & L2E_OFFSET_MASK)) {
- return QCOW2_CLUSTER_UNALLOCATED;
+ /* Offset 0 generally means unallocated, but it is ambiguous with
+ * external data files because 0 is a valid offset there. However, all
+ * clusters in external data files always have refcount 1, so we can
+ * rely on QCOW_OFLAG_COPIED to disambiguate. */
+ if (has_data_file(bs) && (l2_entry & QCOW_OFLAG_COPIED)) {
+ return QCOW2_CLUSTER_NORMAL;
+ } else {
+ return QCOW2_CLUSTER_UNALLOCATED;
+ }
} else {
return QCOW2_CLUSTER_NORMAL;
}
Signed-off-by: Kevin Wolf <kwolf@redhat.com> --- block/qcow2.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)