Small fixes

upstairs/src/dummy_downstairs_tests.rs

@@ -307,10 +307,10 @@ impl DownstairsHandle {
 
     /// Awaits and acks a `Message::Write { .. }` or `Message::Barrier { .. }`
     ///
-    /// Returns the job ID for further checks.
+    /// Returns `true` if the message was a barrier, `false` otherwise
     ///
     /// # Panics
-    /// If a non-write message arrives
+    /// If a message other than `Write` or `Barrier` arrives
     pub async fn ack_write_or_barrier(&mut self) -> bool {
         let (r, was_barrier) = match self.recv().await.unwrap() {
             Message::Write { header, .. } => (

upstairs/src/lib.rs

@@ -1323,6 +1323,11 @@ impl IOop {
                     // the downstairs to act based on that.
                     true
                 }
+                IOop::Barrier { .. } => {
+                    // The Barrier IOop doesn't actually touch any extents; it's
+                    // purely for dependency management.
+                    true
+                }
                 _ => {
                     panic!("Unsupported IO check {:?}", self);
                 }