diff options
| -rw-r--r-- | block/qcow2.h | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/block/qcow2.h b/block/qcow2.h index 7a34bd0c53..8fe2d55005 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -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; } |