fs: add comment explaing File flush is a no-op (#2761)

Signed-off-by: Kruno Tomola Fabro <krunotf@gmail.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/tokio/src/fs/file.rs b/tokio/src/fs/file.rs
index f3bc9854..c44196b3 100644
--- a/tokio/src/fs/file.rs
+++ b/tokio/src/fs/file.rs
@@ -757,6 +757,7 @@ impl AsyncWrite for File {
     }
 
     fn poll_shutdown(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
+        // Flush is a noop for files so it's fine not to call it.
         Poll::Ready(Ok(()))
     }
 }