vm-virtio: fs: Factorize vhost-user setup

This patch factorizes the existing virtio-fs code by relying onto the
common code part of the vhost_user module in the vm-virtio crate.

In details, it factorizes the vhost-user setup, and reuses the error
types defined by the module instead of defining its own types.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vm-virtio/src/vhost_user/mod.rs

@@ -49,6 +49,8 @@ pub enum Error {
     VhostUserCreateMaster(VhostError),
     /// Failed to open vhost device.
     VhostUserOpen(VhostError),
+    /// Connection to socket failed.
+    VhostUserConnect(vhost_rs::Error),
     /// Get features failed.
     VhostUserGetFeatures(VhostError),
     /// Get protocol features failed.
@@ -85,6 +87,10 @@ pub enum Error {
     VhostUserMemoryRegion(MmapError),
     /// Failed to handle vhost-user slave request.
     VhostUserSlaveRequest(vhost_rs::vhost_user::Error),
+    /// Failed to create the master request handler from slave.
+    MasterReqHandlerCreation(vhost_rs::vhost_user::Error),
+    /// Set slave request fd failed.
+    VhostUserSetSlaveRequestFd(vhost_rs::Error),
     /// Invalid used address.
     UsedAddress,
 }