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, 8 insertions, 6 deletions

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 66c71312c381..dcb9a2329e65 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -374,6 +374,7 @@ static void ida_dump(struct ida *ida)
  */
 static struct radix_tree_node *
 radix_tree_node_alloc(gfp_t gfp_mask, struct radix_tree_node *parent,
+                        struct radix_tree_root *root,
                         unsigned int shift, unsigned int offset,
                         unsigned int count, unsigned int exceptional)
 {
@@ -419,11 +420,12 @@ radix_tree_node_alloc(gfp_t gfp_mask, struct radix_tree_node *parent,
 out:
         BUG_ON(radix_tree_is_internal_node(ret));
         if (ret) {
-                ret->parent = parent;
                 ret->shift = shift;
                 ret->offset = offset;
                 ret->count = count;
                 ret->exceptional = exceptional;
+                ret->parent = parent;
+                ret->root = root;
         }
         return ret;
 }
@@ -631,7 +633,7 @@ static int radix_tree_extend(struct radix_tree_root *root, gfp_t gfp,
 
         do {
                 struct radix_tree_node *node = radix_tree_node_alloc(gfp, NULL,
-                                                                shift, 0, 1, 0);
+                                                        root, shift, 0, 1, 0);
                 if (!node)
                         return -ENOMEM;
 
@@ -828,7 +830,7 @@ int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
                 shift -= RADIX_TREE_MAP_SHIFT;
                 if (child == NULL) {
                         /* Have to add a child node.  */
-                        child = radix_tree_node_alloc(gfp, node, shift,
+                        child = radix_tree_node_alloc(gfp, node, root, shift,
                                                         offset, 0, 0);
                         if (!child)
                                 return -ENOMEM;
@@ -1330,7 +1332,7 @@ int radix_tree_split(struct radix_tree_root *root, unsigned long index,
 
         for (;;) {
                 if (node->shift > order) {
-                        child = radix_tree_node_alloc(gfp, node,
+                        child = radix_tree_node_alloc(gfp, node, root,
                                         node->shift - RADIX_TREE_MAP_SHIFT,
                                         offset, 0, 0);
                         if (!child)
@@ -2152,8 +2154,8 @@ void **idr_get_free(struct radix_tree_root *root,
                 shift -= RADIX_TREE_MAP_SHIFT;
                 if (child == NULL) {
                         /* Have to add a child node.  */
-                        child = radix_tree_node_alloc(gfp, node, shift, offset,
-                                                        0, 0);
+                        child = radix_tree_node_alloc(gfp, node, root, shift,
+                                                        offset, 0, 0);
                         if (!child)
                                 return ERR_PTR(-ENOMEM);
                         all_tag_set(child, IDR_FREE);