Ext2FS: Lock a lot. Go way overkill with locking for now.

Kernel/Ext2FileSystem.h

@@ -127,6 +127,8 @@ private:
     mutable ByteBuffer m_cached_super_block;
     mutable ByteBuffer m_cached_group_descriptor_table;
 
+    mutable Lock m_lock;
+
     mutable Lock m_inode_cache_lock;
     mutable HashMap<BlockIndex, RetainPtr<Ext2FSInode>> m_inode_cache;
 };