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Commit 0ac398ef authored by Matthew Wilcox's avatar Matthew Wilcox
Browse files

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: default avatarMatthew Wilcox <mawilcox@microsoft.com>
parent 30b888ba

include/linux/radix-tree.h

+2 −0
Original line number Diff line number Diff line
@@ -311,6 +311,8 @@ void __radix_tree_delete_node(struct radix_tree_root *root, 
			      struct radix_tree_node *node,

			      radix_tree_update_node_t update_node,

			      void *private);

void radix_tree_iter_delete(struct radix_tree_root *,

				struct radix_tree_iter *iter, void **slot);

void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);

void *radix_tree_delete(struct radix_tree_root *, unsigned long);

void radix_tree_clear_tags(struct radix_tree_root *root,

lib/radix-tree.c

+60 −31
Original line number Diff line number Diff line
@@ -581,10 +581,12 @@ static int radix_tree_extend(struct radix_tree_root *root, 
 *	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;

}



/**
@@ -1859,6 +1870,38 @@ 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_iter_delete - delete the entry at this iterator position

 * @root: radix tree root

 * @iter: iterator state

 * @slot: pointer to slot

 *

 * 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
@@ -1867,17 +1910,15 @@ void __radix_tree_delete_node(struct radix_tree_root *root, 
 *

 * 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

 * 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

 * 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)

{