radix-tree: Store a pointer to the root in each node

Instead of having this mysterious private_data in each radix_tree_node,
store a pointer to the root, which can be useful for debugging.  This also
relieves the mm code from the duty of updating it.

Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

1 files changed, 2 insertions, 4 deletions

diff --git a/mm/workingset.c b/mm/workingset.c
index abb58ffa3c64..80c913c89f11 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -354,10 +354,8 @@ void workingset_update_node(struct radix_tree_node *node, void *private)
          * as node->private_list is protected by &mapping->tree_lock.
          */
         if (node->count && node->count == node->exceptional) {
-                if (list_empty(&node->private_list)) {
-                        node->private_data = mapping;
+                if (list_empty(&node->private_list))
                         list_lru_add(&shadow_nodes, &node->private_list);
-                }
         } else {
                 if (!list_empty(&node->private_list))
                         list_lru_del(&shadow_nodes, &node->private_list);
@@ -435,7 +433,7 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
          */
 
         node = container_of(item, struct radix_tree_node, private_list);
-        mapping = node->private_data;
+        mapping = container_of(node->root, struct address_space, page_tree);
 
         /* Coming from the list, invert the lock order */
         if (!spin_trylock(&mapping->tree_lock)) {