Pagecache: Add comments explaining cast

Adds a couple of comments explaining why we're doing a lossy conversion
to Python `int` (saving memory).

volatility3/framework/plugins/linux/pagecache.py

@@ -283,6 +283,10 @@ class Files(plugins.PluginInterface, timeliner.TimeLinerInterface):
                 continue
 
             # Inode already processed?
+            # Store a primitive int (instead of the pointer value) to track
+            # addresses we've already seen. Storing the full `objects.Pointer`
+            # uses too much memory, and we don't need all of the information
+            # that it contains.
             if int(root_inode_ptr) in seen_inodes:
                 continue
 
@@ -319,6 +323,10 @@ class Files(plugins.PluginInterface, timeliner.TimeLinerInterface):
                     continue
 
                 # Inode already processed?
+                # Store a primitive int (instead of the pointer value) to track
+                # addresses we've already seen. Storing the full `objects.Pointer`
+                # uses too much memory, and we don't need all of the information
+                # that it contains.
                 if int(file_inode_ptr) in seen_inodes:
                     continue
                 seen_inodes.add(int(file_inode_ptr))