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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>
This commit is contained in:
Matthew Wilcox 2017-01-28 09:56:22 -05:00
parent 30b888ba95
commit 0ac398ef39
2 changed files with 62 additions and 31 deletions
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2
include/linux/radix-tree.h
View File

@ -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,

91
lib/radix-tree.c
View File

@ -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;
}
/**
@ -1859,25 +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
*
* Returns the address of the deleted item, or NULL if it was not present
* or the entry at the given @index was not @item.
* Remove @item at @index from the radix tree rooted at @root.
*
* 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)
{