Re: [PATCH 1/3] maple_tree: may miss to set node dead on destroy

Wei Yang
2025-02-11T07:48:30Z

On Mon, Feb 10, 2025 at 09:19:46AM -0500, Liam R. Howlett wrote:
>* Wei Yang <richard.weiyang@gmail.com> [250207 20:26]:
>> On destroy, we should set each node dead. But current code miss this
>> when the maple tree has only the root node.
>>
>> The reason is mt_destroy_walk() leverage mte_destroy_descend() to set
>> node dead, but this is skipped since the only root node is a leaf.
>>
>> This patch fixes this by setting the root dead before mt_destroy_walk().
>>
>> Fixes: 54a611b60590 ("Maple Tree: add new data structure")
>> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>> CC: Liam R. Howlett <Liam.Howlett@Oracle.com>
>> Cc: <stable@vger.kernel.org>
>> ---
>> lib/maple_tree.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
>> index 198c14dd3377..d31f0a2858f7 100644
>> --- a/lib/maple_tree.c
>> +++ b/lib/maple_tree.c
>> @@ -5347,6 +5347,8 @@ static inline void mte_destroy_walk(struct maple_enode *enode,
>> {
>> struct maple_node *node = mte_to_node(enode);
>>
>> + mte_set_node_dead(enode);
>> +
>
>This belongs in mt_destroy_walk().

You prefer a change like this?

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index e64ffa5b9970..79f8632c61a3 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5288,6 +5288,7 @@ static void mt_destroy_walk(struct maple_enode *enode, struct maple_tree *mt,
struct maple_enode *start;

if (mte_is_leaf(enode)) {
+ mte_set_node_dead(enode);
node->type = mte_node_type(enode);
goto free_leaf;
}
>
>> if (mt_in_rcu(mt)) {
>> mt_destroy_walk(enode, mt, false);
>> call_rcu(&node->rcu, mt_free_walk);
>> --
>> 2.34.1
>>

--
Wei Yang
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