Mount EFS only once

With this patch, the EFS is only mounted once if it is mountable.  This
significantly reduces bootup time by approximately 0.5 s.

Fixes: #440

CHANGELOG.md

@@ -15,10 +15,12 @@
 - admin-app: Add command to list all supported config fields ([admin-app#28][])
 - admin-app: Add `opcard.disabled` configuration option to disable OpenPGP ([#539][])
 - piv: Use SE050 and encrypt data on external flash ([#534][])
+- Improve external flash mounting to decrease startup time ([#440][])
 
 [admin-app#28]: https://github.com/Nitrokey/admin-app/issues/28
 [fido-authenticator#38]: https://github.com/Nitrokey/fido-authenticator/issues/38
 [piv-authenticator#38]: https://github.com/Nitrokey/piv-authenticator/issues/38
+[#440]: https://github.com/Nitrokey/nitrokey-3-firmware/issues/440
 [#524]: https://github.com/Nitrokey/nitrokey-3-firmware/pull/524
 [#534]: https://github.com/Nitrokey/nitrokey-3-firmware/pull/534
 [#539]: https://github.com/Nitrokey/nitrokey-3-firmware/pull/539

components/boards/src/store.rs

@@ -265,16 +265,17 @@ fn init_efs<B: Board>(
     simulated_efs: bool,
     status: &mut InitStatus,
 ) -> LfsResult<Filesystem<'static, B::ExternalStorage>> {
-    if !Filesystem::is_mountable(efs_storage) {
-        let fmt_ext = Filesystem::format(efs_storage);
+    Filesystem::mount_or_else(efs_alloc, efs_storage, |_err, storage| {
+        error_now!("EFS Mount Error {:?}", _err);
+        let fmt_ext = Filesystem::format(storage);
         if simulated_efs && fmt_ext == Err(littlefs2::io::Error::NO_SPACE) {
             info_now!("Formatting simulated EFS failed as expected");
         } else {
-            error_now!("EFS Mount Error, Reformat {:?}", fmt_ext);
+            error_now!("EFS Reformat {:?}", fmt_ext);
             status.insert(InitStatus::EXTERNAL_FLASH_ERROR);
         }
-    };
-    Filesystem::mount(efs_alloc, efs_storage)
+        Ok(())
+    })
 }
 
 #[inline(always)]