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authorMatthew Wilcox <mawilcox@microsoft.com>2017-01-28 09:56:22 -0500
committerMatthew Wilcox <mawilcox@microsoft.com>2017-02-13 16:09:55 -0500
commit0ac398ef391b53122976325ab6953456ce8e8310 (patch)
tree99318e48860947c93bb7a230e66834abd67bef7a /lib
parent30b888ba950d9f77326b50a4aa2d7d99557d5718 (diff)
downloadlinux-0ac398ef391b53122976325ab6953456ce8e8310.tar.bz2
radix-tree: Add radix_tree_iter_delete
Factor the deletion code out into __radix_tree_delete() and provide a nice iterator-based wrapper around it. If we free the node, advance the iterator to avoid reading from freed memory. Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Diffstat (limited to 'lib')
-rw-r--r--lib/radix-tree.c91
1 files changed, 60 insertions, 31 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 40f3091c5a6b..7bf7d4e60e43 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -581,10 +581,12 @@ out:
* radix_tree_shrink - shrink radix tree to minimum height
* @root radix tree root
*/
-static inline void radix_tree_shrink(struct radix_tree_root *root,
+static inline bool radix_tree_shrink(struct radix_tree_root *root,
radix_tree_update_node_t update_node,
void *private)
{
+ bool shrunk = false;
+
for (;;) {
struct radix_tree_node *node = root->rnode;
struct radix_tree_node *child;
@@ -645,20 +647,26 @@ static inline void radix_tree_shrink(struct radix_tree_root *root,
WARN_ON_ONCE(!list_empty(&node->private_list));
radix_tree_node_free(node);
+ shrunk = true;
}
+
+ return shrunk;
}
-static void delete_node(struct radix_tree_root *root,
+static bool delete_node(struct radix_tree_root *root,
struct radix_tree_node *node,
radix_tree_update_node_t update_node, void *private)
{
+ bool deleted = false;
+
do {
struct radix_tree_node *parent;
if (node->count) {
if (node == entry_to_node(root->rnode))
- radix_tree_shrink(root, update_node, private);
- return;
+ deleted |= radix_tree_shrink(root, update_node,
+ private);
+ return deleted;
}
parent = node->parent;
@@ -672,9 +680,12 @@ static void delete_node(struct radix_tree_root *root,
WARN_ON_ONCE(!list_empty(&node->private_list));
radix_tree_node_free(node);
+ deleted = true;
node = parent;
} while (node);
+
+ return deleted;
}
/**
@@ -1859,25 +1870,55 @@ void __radix_tree_delete_node(struct radix_tree_root *root,
delete_node(root, node, update_node, private);
}
+static bool __radix_tree_delete(struct radix_tree_root *root,
+ struct radix_tree_node *node, void **slot)
+{
+ unsigned offset = get_slot_offset(node, slot);
+ int tag;
+
+ for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
+ node_tag_clear(root, node, tag, offset);
+
+ replace_slot(root, node, slot, NULL, true);
+ return node && delete_node(root, node, NULL, NULL);
+}
+
/**
- * radix_tree_delete_item - delete an item from a radix tree
- * @root: radix tree root
- * @index: index key
- * @item: expected item
+ * radix_tree_iter_delete - delete the entry at this iterator position
+ * @root: radix tree root
+ * @iter: iterator state
+ * @slot: pointer to slot
*
- * Remove @item at @index from the radix tree rooted at @root.
+ * Delete the entry at the position currently pointed to by the iterator.
+ * This may result in the current node being freed; if it is, the iterator
+ * is advanced so that it will not reference the freed memory. This
+ * function may be called without any locking if there are no other threads
+ * which can access this tree.
+ */
+void radix_tree_iter_delete(struct radix_tree_root *root,
+ struct radix_tree_iter *iter, void **slot)
+{
+ if (__radix_tree_delete(root, iter->node, slot))
+ iter->index = iter->next_index;
+}
+
+/**
+ * radix_tree_delete_item - delete an item from a radix tree
+ * @root: radix tree root
+ * @index: index key
+ * @item: expected item
+ *
+ * Remove @item at @index from the radix tree rooted at @root.
*
- * Returns the address of the deleted item, or NULL if it was not present
- * or the entry at the given @index was not @item.
+ * Return: the deleted entry, or %NULL if it was not present
+ * or the entry at the given @index was not @item.
*/
void *radix_tree_delete_item(struct radix_tree_root *root,
unsigned long index, void *item)
{
struct radix_tree_node *node;
- unsigned int offset;
void **slot;
void *entry;
- int tag;
entry = __radix_tree_lookup(root, index, &node, &slot);
if (!entry)
@@ -1886,32 +1927,20 @@ void *radix_tree_delete_item(struct radix_tree_root *root,
if (item && entry != item)
return NULL;
- if (!node) {
- root_tag_clear_all(root);
- root->rnode = NULL;
- return entry;
- }
-
- offset = get_slot_offset(node, slot);
-
- /* Clear all tags associated with the item to be deleted. */
- for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
- node_tag_clear(root, node, tag, offset);
-
- __radix_tree_replace(root, node, slot, NULL, NULL, NULL);
+ __radix_tree_delete(root, node, slot);
return entry;
}
EXPORT_SYMBOL(radix_tree_delete_item);
/**
- * radix_tree_delete - delete an item from a radix tree
- * @root: radix tree root
- * @index: index key
+ * radix_tree_delete - delete an entry from a radix tree
+ * @root: radix tree root
+ * @index: index key
*
- * Remove the item at @index from the radix tree rooted at @root.
+ * Remove the entry at @index from the radix tree rooted at @root.
*
- * Returns the address of the deleted item, or NULL if it was not present.
+ * Return: The deleted entry, or %NULL if it was not present.
*/
void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
{