agent: replace if let Err with or_else

Fixes #934

Signed-off-by: Tim Zhang <tim@hyper.sh>

src/agent/rustjail/src/container.rs

@@ -487,23 +487,26 @@ fn do_init_child(cwfd: RawFd) -> Result<()> {
         }
 
         log_child!(cfd_log, "join namespace {:?}", s);
-        if let Err(e) = sched::setns(fd, s) {
+        sched::setns(fd, s).or_else(|e| {
             if s == CloneFlags::CLONE_NEWUSER {
                 if e.as_errno().unwrap() != Errno::EINVAL {
                     check!(
                         write_sync(cwfd, SYNC_FAILED, format!("{:?}", e).as_str()),
                         "write_sync for CLONE_NEWUSER"
                     );
-                    return Err(e.into());
+                    return Err(e);
                 }
+
+                Ok(())
             } else {
                 check!(
                     write_sync(cwfd, SYNC_FAILED, format!("{:?}", e).as_str()),
                     "write_sync for sched::setns"
                 );
-                return Err(e.into());
+                Err(e)
             }
-        }
+        })?;
+
         unistd::close(fd)?;
 
         if s == CloneFlags::CLONE_NEWUSER {

src/agent/src/mount.rs

@@ -479,15 +479,18 @@ fn mount_to_rootfs(logger: &Logger, m: &INIT_MOUNT) -> Result<()> {
 
     fs::create_dir_all(Path::new(m.dest)).context("could not create directory")?;
 
-    if let Err(err) = bare_mount.mount() {
+    bare_mount.mount().or_else(|e| {
         if m.src != "dev" {
-            return Err(err.into());
+            return Err(e);
         }
+
         error!(
             logger,
             "Could not mount filesystem from {} to {}", m.src, m.dest
         );
-    }
+
+        Ok(())
+    })?;
 
     Ok(())
 }

src/agent/src/rpc.rs

@@ -1610,11 +1610,13 @@ fn do_copy_file(req: &CopyFileRequest) -> Result<()> {
         PathBuf::from("/")
     };
 
-    if let Err(e) = fs::create_dir_all(dir.to_str().unwrap()) {
+    fs::create_dir_all(dir.to_str().unwrap()).or_else(|e| {
         if e.kind() != std::io::ErrorKind::AlreadyExists {
-            return Err(e.into());
+            return Err(e);
         }
-    }
+
+        Ok(())
+    })?;
 
     std::fs::set_permissions(
         dir.to_str().unwrap(),