vhost_user_block: Make Error behave like net and fs versions

Make the Error struct behave more like the net and fs equivalents.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

vhost_user_block/src/lib.rs

@@ -32,6 +32,7 @@ use vhost_user_backend::{VhostUserBackend, VhostUserDaemon, Vring, VringWorker};
 use virtio_bindings::bindings::virtio_blk::*;
 use vm_memory::{Bytes, GuestMemoryError, GuestMemoryMmap};
 use vm_virtio::block::{build_disk_image_id, Request};
+use std::{fmt, error, convert,io};
 
 const QUEUE_SIZE: usize = 1024;
 const SECTOR_SHIFT: u8 = 9;
@@ -64,6 +65,20 @@ pub enum Error {
     ParseBlkNumQueuesParam(std::num::ParseIntError),
 }
 
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "vhost_user_block_error: {:?}", self)
+    }
+}
+
+impl error::Error for Error {}
+
+impl convert::From<Error> for io::Error {
+    fn from(e: Error) -> Self {
+        io::Error::new(io::ErrorKind::Other, e)
+    }
+}
+
 pub struct VhostUserBlkBackend {
     mem: Option<GuestMemoryMmap>,
     vring_worker: Option<Arc<VringWorker>>,