fs: preserve max_buf_size when cloning a File (#7593)

Author: martin-g

tokio/src/fs/file.rs

@@ -465,7 +465,9 @@ impl File {
         self.inner.lock().await.complete_inflight().await;
         let std = self.std.clone();
         let std_file = asyncify(move || std.try_clone()).await?;
-        Ok(File::from_std(std_file))
+        let mut file = File::from_std(std_file);
+        file.set_max_buf_size(self.max_buf_size);
+        Ok(file)
     }
 
     /// Destructures `File` into a [`std::fs::File`]. This function is

tokio/tests/fs.rs

@@ -15,6 +15,22 @@ async fn path_read_write() {
     assert_eq!(out, b"bytes");
 }
 
+#[tokio::test]
+async fn try_clone_should_preserve_max_buf_size() {
+    let buf_size = 128;
+    let temp = tempdir();
+    let dir = temp.path();
+
+    let mut file = fs::File::create(dir.join("try_clone_should_preserve_max_buf_size"))
+        .await
+        .unwrap();
+    file.set_max_buf_size(buf_size);
+
+    let cloned = file.try_clone().await.unwrap();
+
+    assert_eq!(cloned.max_buf_size(), buf_size);
+}
+
 fn tempdir() -> tempfile::TempDir {
     tempfile::tempdir().unwrap()
 }