1 files changed, 5 insertions, 0 deletions
diff --git a/include/block/block-common.h b/include/block/block-common.h
index e15395f2cb..df5ffc8d09 100644
--- a/include/block/block-common.h
+++ b/include/block/block-common.h
@@ -132,6 +132,11 @@ typedef struct BlockZoneWps {
 typedef struct BlockDriverInfo {
     /* in bytes, 0 if irrelevant */
     int cluster_size;
+    /*
+     * A fraction of cluster_size, if supported (currently QCOW2 only); if
+     * disabled or unsupported, set equal to cluster_size.
+     */
+    int subcluster_size;
     /* offset at which the VM state can be saved (0 if not possible) */
     int64_t vm_state_offset;
     bool is_dirty;