retry file copies during migration (#1221)

* retry file copies during migration up to 10x

* fix build

* readonly mounts, and validation on v2 recovery

* banish booleans

backend/src/disk/mount/filesystem/mod.rs

@@ -12,8 +12,20 @@ pub mod cifs;
 pub mod ecryptfs;
 pub mod label;
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum MountType {
+    ReadOnly,
+    ReadWrite,
+}
+
+pub use MountType::*;
+
 #[async_trait]
 pub trait FileSystem {
-    async fn mount<P: AsRef<Path> + Send + Sync>(&self, mountpoint: P) -> Result<(), Error>;
+    async fn mount<P: AsRef<Path> + Send + Sync>(
+        &self,
+        mountpoint: P,
+        mount_type: MountType,
+    ) -> Result<(), Error>;
     async fn source_hash(&self) -> Result<GenericArray<u8, <Sha256 as Digest>::OutputSize>, Error>;
 }