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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@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox 2016-12-14 15:08:34 -08:00 committed by Linus Torvalds
parent 91b9677c4c
commit 91d9c05ac6
2 changed files with 5 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
include/linux/radix-tree.h
View File

@ -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];
};

1
lib/radix-tree.c
View File

@ -325,6 +325,7 @@ static void radix_tree_node_rcu_free(struct rcu_head *head)
tag_clear(node, i, 0);
node->slots[0] = NULL;
INIT_LIST_HEAD(&node->private_list);
kmem_cache_free(radix_tree_node_cachep, node);
}