[PATCH 3/3] maple_tree: assert retrieving new value on a tree with only root node

[Wei Yang]

On Mon, Feb 10, 2025 at 09:18:53AM -0500, Liam R. Howlett wrote:
>* Wei Yang <richard.weiyang at gmail.com> [250207 20:26]:
>> Original code may get a stall value when overwriting the whole range on a
>                          ^^^^^- stale value.  I thought you were saying
>			  it was stalling which did not make sense.
>

I want to say we don't get the new value as we expect.

How about:

Original code may not get the new value after overwriting the whole range on a
maple tree with only root node.

>> maple tree with only root node. The reason is we didn't set the only
>> root node dead during destroy.
>> 
>> Add a test case to verify this is not recreated.
>> 
>> Signed-off-by: Wei Yang <richard.weiyang at gmail.com>
>> CC: Liam R. Howlett <Liam.Howlett at Oracle.com>
>> ---
>>  tools/testing/radix-tree/maple.c | 24 ++++++++++++++++++++++++
>>  1 file changed, 24 insertions(+)
>> 
>> diff --git a/tools/testing/radix-tree/maple.c b/tools/testing/radix-tree/maple.c
>> index bc30050227fd..1e293e4d856d 100644
>> --- a/tools/testing/radix-tree/maple.c
>> +++ b/tools/testing/radix-tree/maple.c
>> @@ -35256,6 +35256,30 @@ static noinline void __init check_rcu_simulated(struct maple_tree *mt)
>>  	MT_BUG_ON(mt, mas_prev(&mas_reader, 0) != xa_mk_value(val));
>>  	rcu_read_unlock();
>>  
>> +	/* Clear out tree & create one with only root node */
>> +	mas_lock(&mas_writer);
>> +	mas_set_range(&mas_writer, 0, ULONG_MAX);
>> +	mas_store_gfp(&mas_writer, NULL, GFP_KERNEL);
>> +	mas_set_range(&mas_writer, 0, 0);
>> +	for (i = 0; i <= 5; i++) {
>> +		mas_writer.index = i * 10;
>> +		mas_writer.last = i * 10 + 5;
>> +		mas_store_gfp(&mas_writer, xa_mk_value(i), GFP_KERNEL);
>> +	}
>> +	mas_unlock(&mas_writer);
>> +	target = 10;
>> +	mas_set_range(&mas_reader, target, target);
>> +	rcu_read_lock();
>> +	MT_BUG_ON(mt, mas_walk(&mas_reader) != xa_mk_value(target/10));
>> +
>> +	/* Overwrite the whole range */
>> +	mas_lock(&mas_writer);
>> +	mas_set_range(&mas_writer, 0, ULONG_MAX);
>> +	mas_store_gfp(&mas_writer, xa_mk_value(val), GFP_KERNEL);
>> +	mas_unlock(&mas_writer);
>> +	MT_BUG_ON(mt, mas_walk(&mas_reader) != xa_mk_value(val));
>> +	rcu_read_unlock();
>> +
>>  	rcu_unregister_thread();
>>  }
>>  
>> -- 
>> 2.34.1
>> 

-- 
Wei Yang
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