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

[Wei Yang <richard.weiyang@gmail.com>]

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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