From: Matthew Wilcox <willy@xxxxxxxxxxxxx> Subject: radix-tree: move rcu_head into a union with private_list 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. Link: http://lkml.kernel.org/r/1480369871-5271-50-git-send-email-mawilcox@xxxxxxxxxxxxxxxxx Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> Tested-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx> Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> Cc: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/radix-tree.h | 14 ++++---------- lib/radix-tree.c | 1 + 2 files changed, 5 insertions(+), 10 deletions(-) diff -puN include/linux/radix-tree.h~radix-tree-move-rcu_head-into-a-union-with-private_list include/linux/radix-tree.h --- a/include/linux/radix-tree.h~radix-tree-move-rcu_head-into-a-union-with-private_list +++ a/include/linux/radix-tree.h @@ -85,18 +85,12 @@ struct radix_tree_node { unsigned char offset; /* Slot offset in parent */ unsigned char count; /* Total entry count */ unsigned char exceptional; /* Exceptional entry 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 -puN lib/radix-tree.c~radix-tree-move-rcu_head-into-a-union-with-private_list lib/radix-tree.c --- a/lib/radix-tree.c~radix-tree-move-rcu_head-into-a-union-with-private_list +++ a/lib/radix-tree.c @@ -325,6 +325,7 @@ static void radix_tree_node_rcu_free(str tag_clear(node, i, 0); node->slots[0] = NULL; + INIT_LIST_HEAD(&node->private_list); kmem_cache_free(radix_tree_node_cachep, node); } _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
