[PATCH v5 5/5] maple_tree: add a test checking storing null

[Wei Yang]

On Thu, Oct 31, 2024 at 08:37:57PM -0700, Andrew Morton wrote:
>On Thu, 31 Oct 2024 23:16:27 +0000 Wei Yang <richard.weiyang at gmail.com> wrote:
>
>> Add a test to assert that, when storing null to am empty tree or a
>> single entry tree it will not result into:
>> 
>>   * a root node with range [0, ULONG_MAX] set to NULL
>>   * a root node with consecutive slot set to NULL
>> 
>
>I don't get it.
>

For example, if we store NULL to [3, 10] currently, we will have a root node
like this.

maple_tree(0x7fff2b797170) flags 5, height 1 root 0x615000000d0e
0-18446744073709551615: node 0x615000000d00 depth 0 type 1 parent 0x7fff2b797171 contents: (nil) 2 (nil) 10 (nil) 18446744073709551615 (nil) 0 (nil) 0 (nil) 0 (nil) 0 (nil) 0 (nil) 0 (nil) 0 (nil) 0 (nil) 0 (nil) 0 (nil) 0 (nil) 0 0x2
  0-2: (nil)
  3-10: (nil)
  11-18446744073709551615: (nil)

Slot 0, 1 is consecutively set to NULL. This is not expected.

>> --- a/lib/test_maple_tree.c
>> +++ b/lib/test_maple_tree.c
>> @@ -1387,6 +1387,92 @@ static noinline void __init check_prev_entry(struct maple_tree *mt)
>>  	mas_unlock(&mas);
>>  }
>>  
>> +static noinline void __init check_store_null(struct maple_tree *mt)
>> +{
>> +	MA_STATE(mas, mt, 0, ULONG_MAX);
>> +
>>
>> ...
>>
>> +	MT_BUG_ON(mt, !xa_is_node(mas_root(&mas)));
>> ...
>>
>
>mas_root() is private to lib/maple_tree.c.  I'll do this for now:

Oh, thanks.

>
>--- a/lib/test_maple_tree.c~maple_tree-add-a-test-checking-storing-null-fix
>+++ a/lib/test_maple_tree.c
>@@ -1453,7 +1453,7 @@ static noinline void __init check_store_
> 	mas_set_range(&mas, 2, 5);
> 	mas_store_gfp(&mas, NULL, GFP_KERNEL);
> 	MT_BUG_ON(mt, mtree_empty(mt));
>-	MT_BUG_ON(mt, xa_is_node(mas_root(&mas)));
>+//	MT_BUG_ON(mt, xa_is_node(mas_root(&mas)));
> 	mas_unlock(&mas);
> 	mtree_destroy(mt);
> 
>@@ -1465,7 +1465,7 @@ static noinline void __init check_store_
> 	mas_lock(&mas);
> 	mas_set_range(&mas, 1, 3);
> 	mas_store_gfp(&mas, &mas, GFP_KERNEL);
>-	MT_BUG_ON(mt, !xa_is_node(mas_root(&mas)));
>+//	MT_BUG_ON(mt, !xa_is_node(mas_root(&mas)));
> 	mas_set_range(&mas, 0, ULONG_MAX);
> 	mas_store_gfp(&mas, NULL, GFP_KERNEL);
> 	MT_BUG_ON(mt, !mtree_empty(mt));
>_

-- 
Wei Yang
Help you, Help me