1 files changed, 7 insertions, 0 deletions
diff --git a/block.c b/block.c
index a307c151a8..0af890f647 100644
--- a/block.c
+++ b/block.c
@@ -6480,6 +6480,13 @@ int coroutine_fn bdrv_co_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
     }
     memset(bdi, 0, sizeof(*bdi));
     ret = drv->bdrv_co_get_info(bs, bdi);
+    if (bdi->subcluster_size == 0) {
+        /*
+         * If the driver left this unset, subclusters are not supported.
+         * Then it is safe to treat each cluster as having only one subcluster.
+         */
+        bdi->subcluster_size = bdi->cluster_size;
+    }
     if (ret < 0) {
         return ret;
     }