Add basic umnount function

src/main.rs

@@ -53,6 +53,14 @@ impl vfs_rpc::Server for Serv {
             Ok((fs_pid, fd))
         }
     }
+
+    fn unmount(&self, path: &Path) -> Result<(), ()> {
+        if self.mount_list.write().remove(path).is_none() {
+            Err(())
+        } else {
+            Ok(())
+        }
+    }
 }
 
 fn main() {

vfs_rpc/src/lib.rs

@@ -15,6 +15,7 @@ pub trait Server: Send + Sync {
     fn register_fs(&self, from: u64, kind: &str) -> Result<(), ()>;
     fn mount(&self, dev: &Path, kind: &str, path: &Path) -> Result<(), ()>;
     fn open(&self, path: &Path) -> Result<(u64, u64), ()>;
+    fn unmount(&self, path: &Path) -> Result<(), ()>;
 }
 
 #[derive(Copy, Clone)]
@@ -51,6 +52,19 @@ impl Client {
         )
         .unwrap()
     }
+
+    pub fn unmount(self, path: &Path) -> Result<(), ()> {
+        postcard::from_bytes(
+            &rpc::send_call(
+                self.0,
+                PROTO,
+                3,
+                &postcard::to_stdvec(path).unwrap(),
+            )
+            .get_return(),
+        )
+        .unwrap()
+    }
 }
 
 pub fn register_server(server: Box<dyn Server>) {
@@ -78,5 +92,9 @@ fn callback(call: IncomingCall) {
         let path = postcard::from_bytes(call.args()).unwrap();
         let ret = postcard::to_stdvec(&server.open(path)).unwrap();
         call.send_return(&ret);
+    }  else if call.func == 3 {
+        let path = postcard::from_bytes(call.args()).unwrap();
+        let ret = postcard::to_stdvec(&server.unmount(path)).unwrap();
+        call.send_return(&ret);
     }
 }