1 files changed, 2 insertions, 0 deletions
diff --git a/block_int.h b/block_int.h
index ea818e4e71..311bd2a6fa 100644
--- a/block_int.h
+++ b/block_int.h
@@ -198,6 +198,8 @@ struct BlockDriverState {
     int encrypted; /* if true, the media is encrypted */
     int valid_key; /* if true, a valid encryption key has been set */
     int sg;        /* if true, the device is a /dev/sg* */
+    int copy_on_read; /* if true, copy read backing sectors into image
+                         note this is a reference count */
 
     BlockDriver *drv; /* NULL means no media */
     void *opaque;