feat(ext4): seek, rmdir (e2fsck-clean)

crates/servers/storage-server/src/filesystem.rs

@@ -74,6 +74,10 @@ pub trait FileSystem {
     fn delete(&mut self, path: &[u8]) -> bool;
     fn file_size(&mut self, handle: FileHandle) -> Option<usize>;
     fn mkdir(&mut self, path: &[u8]) -> bool;
+    /// Moves `handle`'s position to `offset` (at most the file's size).
+    fn seek(&mut self, handle: FileHandle, offset: usize) -> bool;
+    /// Removes the directory at `path`, which must be empty.
+    fn rmdir(&mut self, path: &[u8]) -> bool;
     /// Whether anything can be written at all; the server refuses
     /// writing requests up front when not.
     fn writable(&self) -> bool {