block: qcow_async: impl DiskFd for QcowDiskAsync

Returns a borrowed file descriptor for the underlying data file.

Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>

block/src/qcow_async.rs

@@ -8,8 +8,10 @@
 
 use std::fmt;
 use std::fs::File;
+use std::os::fd::{AsFd, AsRawFd};
 use std::sync::Arc;
 
+use crate::async_io::BorrowedDiskFd;
 use crate::disk_file;
 use crate::error::{BlockErrorKind, BlockResult, ErrorOp};
 use crate::qcow::backing::shared_backing_from;
@@ -81,3 +83,9 @@ impl disk_file::PhysicalSize for QcowDiskAsync {
         Ok(self.data_raw_file.physical_size()?)
     }
 }
+
+impl disk_file::DiskFd for QcowDiskAsync {
+    fn fd(&self) -> BorrowedDiskFd<'_> {
+        BorrowedDiskFd::new(self.data_raw_file.as_fd().as_raw_fd())
+    }
+}