From: Matthew Wilcox <willy@xxxxxxxxxxxxx>
I want to be able to reference node->parent after freeing node.
Currently node->parent is in a union with rcu_head, so it is overwritten
when the node is put on the RCU list. We know that private_list is not
referenced after the node is freed, so it is safe for these two members
to share space.
Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
---
include/linux/radix-tree.h | 14 ++++----------
lib/radix-tree.c | 1 +
2 files changed, 5 insertions(+), 10 deletions(-)
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 8ffb051..66fb8c0 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -88,18 +88,12 @@ struct radix_tree_node {
unsigned char shift; /* Bits remaining in each slot */
unsigned char offset; /* Slot offset in parent */
unsigned int count;
+ struct radix_tree_node *parent; /* Used when ascending tree */
+ void *private_data; /* For tree user */
union {
- struct {
- /* Used when ascending tree */
- struct radix_tree_node *parent;
- /* For tree user */
- void *private_data;
- };
- /* Used when freeing node */
- struct rcu_head rcu_head;
+ struct list_head private_list; /* For tree user */
+ struct rcu_head rcu_head; /* Used when freeing node */
};
- /* For tree user */
- struct list_head private_list;
void __rcu *slots[RADIX_TREE_MAP_SIZE];
unsigned long tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
};
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index e917c56..baf4ba1 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -325,6 +325,7 @@ static void radix_tree_node_rcu_free(struct rcu_head *head)
*/
memset(node->slots, 0, sizeof(node->slots));
memset(node->tags, 0, sizeof(node->tags));
+ INIT_LIST_HEAD(&node->private_list);
kmem_cache_free(radix_tree_node_cachep, node);
}
--
2.10.2
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