mm/workingset: Do not protect workingset_shadow_nodes with irq off

workingset_shadow_nodes is protected by local_irq_disable(). Some users
use spin_lock_irq().
Replace the irq/on with a local_lock(). Rename workingset_shadow_nodes
so I catch users of it which will be introduced later.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
diff --git a/mm/filemap.c b/mm/filemap.c
index 50b52fe..f4f5e7e56 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -159,9 +159,12 @@
 		 * node->private_list is protected by
 		 * mapping->tree_lock.
 		 */
-		if (!list_empty(&node->private_list))
-			list_lru_del(&workingset_shadow_nodes,
+		if (!list_empty(&node->private_list)) {
+			local_lock(workingset_shadow_lock);
+			list_lru_del(&__workingset_shadow_nodes,
 				     &node->private_list);
+			local_unlock(workingset_shadow_lock);
+		}
 	}
 	return 0;
 }
@@ -217,8 +220,10 @@
 		if (!dax_mapping(mapping) && !workingset_node_pages(node) &&
 				list_empty(&node->private_list)) {
 			node->private_data = mapping;
-			list_lru_add(&workingset_shadow_nodes,
-					&node->private_list);
+			local_lock(workingset_shadow_lock);
+			list_lru_add(&__workingset_shadow_nodes,
+				     &node->private_list);
+			local_unlock(workingset_shadow_lock);
 		}
 	}