Simplify DiskWriter poll_flush

src/cache/fs.rs

@@ -331,14 +331,9 @@ impl AsyncWrite for EncryptedDiskWriter {
     }
 
     #[inline]
-    fn poll_flush(
-        mut self: Pin<&mut Self>,
-        cx: &mut Context<'_>,
-    ) -> Poll<Result<(), std::io::Error>> {
-        if self.buffer.is_empty() {
-            self.as_mut().file.as_mut().poll_flush(cx)
-        } else {
+    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), std::io::Error>> {
         let pinned = Pin::into_inner(self);
+
         while !pinned.buffer.is_empty() {
             match pinned.file.as_mut().poll_write(cx, &pinned.buffer) {
                 Poll::Ready(Ok(n)) => {
@@ -349,8 +344,7 @@ impl AsyncWrite for EncryptedDiskWriter {
             }
         }
 
-            Poll::Ready(Ok(()))
-        }
+        pinned.file.as_mut().poll_flush(cx)
     }
 
     #[inline]