devices: block: sync after setting refcount

Make sure that the refcount update is commited to disk before we start
to write data to the cluster.

Change-Id: Ibdf5dde7a75c3582f87df46af1095c7dc0007d98
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1136019
Reviewed-by: Stephen Barber <smbarber@chromium.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/qcow/src/qcow.rs b/qcow/src/qcow.rs
index 2052545..d4cb6af 100644
--- a/qcow/src/qcow.rs
+++ b/qcow/src/qcow.rs
@@ -411,6 +411,8 @@ impl QcowFile {
         self.file.sync_data()?;
         // The cluster refcount starts at one indicating it is used but doesn't need COW.
         self.set_cluster_refcount(new_addr, 1)?;
+        // Ensure that the refcount is updated before starting to use the cluster.
+        self.file.sync_data()?;
         Ok(new_addr)
     }