[PATCH v3 26/33] radix-tree: Fix replacement for multiorder entries

Matthew Wilcox
2016-11-28T20:05:37Z

From: Matthew Wilcox <mawilcox@microsoft.com>

When replacing an entry with NULL, we need to delete any sibling entries.
Also account deleting exceptional entries properly.
Also fix a bug with radix_tree_iter_replace() where we would fail to
remove entirely freed nodes.
Also fix accounting bug when switching between normal and exceptional
entries with replace_slot.
Also add testcases for all these bugs.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
lib/radix-tree.c | 60 +++++++++++++++++-------
tools/testing/radix-tree/multiorder.c | 87 ++++++++++++++++++++++++++++++-----
2 files changed, 119 insertions(+), 28 deletions(-)

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 9d24bec..a227727 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -976,6 +976,24 @@ void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
}
EXPORT_SYMBOL(radix_tree_lookup);

+static inline int slot_count(struct radix_tree_node *node,
+ void **slot)
+{
+ int n = 1;
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+ void *ptr = node_to_entry(slot);
+ unsigned offset = get_slot_offset(node, slot);
+ int i;
+
+ for (i = 1; offset + i < RADIX_TREE_MAP_SIZE; i++) {
+ if (node->slots[offset + i] != ptr)
+ break;
+ n++;
+ }
+#endif
+ return n;
+}
+
static void replace_slot(struct radix_tree_root *root,
struct radix_tree_node *node,
void **slot, void *item,
@@ -994,12 +1012,35 @@ static void replace_slot(struct radix_tree_root *root,

if (node) {
node->count += count;
- node->exceptional += exceptional;
+ if (exceptional) {
+ exceptional *= slot_count(node, slot);
+ node->exceptional += exceptional;
+ }
}

rcu_assign_pointer(*slot, item);
}

+static inline void delete_sibling_entries(struct radix_tree_node *node,
+ void **slot)
+{
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+ bool exceptional = radix_tree_exceptional_entry(*slot);
+ void *ptr = node_to_entry(slot);
+ unsigned offset = get_slot_offset(node, slot);
+ int i;
+
+ for (i = 1; offset + i < RADIX_TREE_MAP_SIZE; i++) {
+ if (node->slots[offset + i] != ptr)
+ break;
+ node->slots[offset + i] = NULL;
+ node->count--;
+ if (exceptional)
+ node->exceptional--;
+ }
+#endif
+}
+
/**
* __radix_tree_replace - replace item in a slot
* @root: radix tree root
@@ -1017,6 +1058,8 @@ void __radix_tree_replace(struct radix_tree_root *root,
void **slot, void *item,
radix_tree_update_node_t update_node, void *private)
{
+ if (!item)
+ delete_sibling_entries(node, slot);
/*
* This function supports replacing exceptional entries and
* deleting entries, but that needs accounting against the
@@ -1793,20 +1836,6 @@ void __radix_tree_delete_node(struct radix_tree_root *root,
delete_node(root, node, NULL, NULL);
}

-static inline void delete_sibling_entries(struct radix_tree_node *node,
- void *ptr, unsigned offset)
-{
-#ifdef CONFIG_RADIX_TREE_MULTIORDER
- int i;
- for (i = 1; offset + i < RADIX_TREE_MAP_SIZE; i++) {
- if (node->slots[offset + i] != ptr)
- break;
- node->slots[offset + i] = NULL;
- node->count--;
- }
-#endif
-}
-
/**
* radix_tree_delete_item - delete an item from a radix tree
* @root: radix tree root
@@ -1846,7 +1875,6 @@ void *radix_tree_delete_item(struct radix_tree_root *root,
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
node_tag_clear(root, node, tag, offset);

- delete_sibling_entries(node, node_to_entry(slot), offset);
__radix_tree_replace(root, node, slot, NULL, NULL, NULL);

return entry;
diff --git a/tools/testing/radix-tree/multiorder.c b/tools/testing/radix-tree/multiorder.c
index 5421f01..9757b89 100644
--- a/tools/testing/radix-tree/multiorder.c
+++ b/tools/testing/radix-tree/multiorder.c
@@ -410,8 +410,6 @@ static void __multiorder_split(int old_order, int new_order)
RADIX_TREE(tree, GFP_ATOMIC);
void **slot;
struct radix_tree_iter iter;
- struct radix_tree_node *node;
- void *item;
unsigned alloc;

radix_tree_preload(GFP_KERNEL);
@@ -434,58 +432,122 @@ static void __multiorder_split(int old_order, int new_order)
radix_tree_preload_end();

item_kill_tree(&tree);
+}
+
+static void __multiorder_split2(int old_order, int new_order)
+{
+ RADIX_TREE(tree, GFP_KERNEL);
+ void **slot;
+ struct radix_tree_iter iter;
+ struct radix_tree_node *node;
+ void *item;

- radix_tree_preload(GFP_KERNEL);
__radix_tree_insert(&tree, 0, old_order, (void *)0x12);
- radix_tree_preload_end();

item = __radix_tree_lookup(&tree, 0, &node, NULL);
assert(item == (void *)0x12);
assert(node->exceptional > 0);

- radix_tree_split_preload(old_order, new_order, GFP_KERNEL);
radix_tree_split(&tree, 0, new_order);
radix_tree_for_each_slot(slot, &tree, &iter, 0) {
radix_tree_iter_replace(&tree, &iter, slot,
item_create(iter.index, new_order));
}
- radix_tree_preload_end();

item = __radix_tree_lookup(&tree, 0, &node, NULL);
assert(item != (void *)0x12);
assert(node->exceptional == 0);

item_kill_tree(&tree);
+}
+
+static void __multiorder_split3(int old_order, int new_order)
+{
+ RADIX_TREE(tree, GFP_KERNEL);
+ void **slot;
+ struct radix_tree_iter iter;
+ struct radix_tree_node *node;
+ void *item;

- radix_tree_preload(GFP_KERNEL);
__radix_tree_insert(&tree, 0, old_order, (void *)0x12);
- radix_tree_preload_end();

item = __radix_tree_lookup(&tree, 0, &node, NULL);
assert(item == (void *)0x12);
assert(node->exceptional > 0);

- radix_tree_split_preload(old_order, new_order, GFP_KERNEL);
radix_tree_split(&tree, 0, new_order);
radix_tree_for_each_slot(slot, &tree, &iter, 0) {
radix_tree_iter_replace(&tree, &iter, slot, (void *)0x16);
}
- radix_tree_preload_end();

item = __radix_tree_lookup(&tree, 0, &node, NULL);
assert(item == (void *)0x16);
assert(node->exceptional > 0);

item_kill_tree(&tree);
+
+ __radix_tree_insert(&tree, 0, old_order, (void *)0x12);
+
+ item = __radix_tree_lookup(&tree, 0, &node, NULL);
+ assert(item == (void *)0x12);
+ assert(node->exceptional > 0);
+
+ radix_tree_split(&tree, 0, new_order);
+ radix_tree_for_each_slot(slot, &tree, &iter, 0) {
+ if (iter.index == (1 << new_order))
+ radix_tree_iter_replace(&tree, &iter, slot,
+ (void *)0x16);
+ else
+ radix_tree_iter_replace(&tree, &iter, slot, NULL);
+ }
+
+ item = __radix_tree_lookup(&tree, 1 << new_order, &node, NULL);
+ assert(item == (void *)0x16);
+ assert(node->count == node->exceptional);
+ do {
+ node = node->parent;
+ if (!node)
+ break;
+ assert(node->count == 1);
+ assert(node->exceptional == 0);
+ } while (1);
+
+ item_kill_tree(&tree);
}

static void multiorder_split(void)
{
int i, j;

- for (i = 9; i < 19; i++)
- for (j = 0; j < i; j++)
+ for (i = 3; i < 11; i++)
+ for (j = 0; j < i; j++) {
__multiorder_split(i, j);
+ __multiorder_split2(i, j);
+ __multiorder_split3(i, j);
+ }
+}
+
+static void multiorder_account(void)
+{
+ RADIX_TREE(tree, GFP_KERNEL);
+ struct radix_tree_node *node;
+ void **slot;
+
+ item_insert_order(&tree, 0, 5);
+
+ __radix_tree_insert(&tree, 1 << 5, 5, (void *)0x12);
+ __radix_tree_lookup(&tree, 0, &node, NULL);
+ assert(node->count == node->exceptional * 2);
+ radix_tree_delete(&tree, 1 << 5);
+ assert(node->exceptional == 0);
+
+ __radix_tree_insert(&tree, 1 << 5, 5, (void *)0x12);
+ __radix_tree_lookup(&tree, 1 << 5, &node, &slot);
+ assert(node->count == node->exceptional * 2);
+ __radix_tree_replace(&tree, node, slot, NULL, NULL, NULL);
+ assert(node->exceptional == 0);
+
+ item_kill_tree(&tree);
}

void multiorder_checks(void)
@@ -507,6 +569,7 @@ void multiorder_checks(void)
multiorder_tagged_iteration();
multiorder_join();
multiorder_split();
+ multiorder_account();

radix_tree_cpu_dead(0);
}
--
2.10.2