On Thu, Oct 17, 2024 at 10:10:20AM -0400, Liam R. Howlett wrote:
>* Wei Yang <richard.weiyang@xxxxxxxxx> [241017 09:46]:
>> Currently, when storing NULL on mas_root_expand(), the behavior could be
>> improved.
>>
>> For example possible cases are:
>>
>> * store NULL at any range result a new node
>> * store NULL at range [m, n] where m > 0 to a single entry tree result
>> a new node with range [m, n] set to NULL
>> * store NULL at range [m, n] where m > 0 to an empty tree result
>> consecutive NULL slot
>>
>> This patch tries to improve in:
>>
>> * memory efficient by setting to empty tree instead of using a node
>> * remove the possibility of consecutive NULL slot which will prohibit
>> extended null in later operation
>>
>> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
>> CC: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
>> CC: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
>> CC: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
>> ---
>> lib/maple_tree.c | 18 ++++++++++++++++++
>> 1 file changed, 18 insertions(+)
>>
>> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
>> index a90c29156fe2..15d2124acc36 100644
>> --- a/lib/maple_tree.c
>> +++ b/lib/maple_tree.c
>> @@ -3335,6 +3335,24 @@ static inline void mas_root_expand(struct ma_state *mas, void *entry)
>> unsigned long *pivots;
>> int slot = 0;
>>
>> + if (!entry) {
>> + /*
>> + * We come here in two cases:
>> + * 1. This is an empty tree
>> + * 2. This is a single entry tree with range [0, 0]
>> + *
>> + * If this is an empty tree, the result should still be an
>> + * empty tree no matter what the range is.
>> + *
>> + * If this is a single entry tree, we should set it to an
>> + * empty tree if the range cover [0, 0]. Otherwise, we don't
>> + * need to change it.
>> + */
>> + if (!mas->index && contents)
>> + rcu_assign_pointer(mas->tree->ma_root, NULL);
>> + return;
>> + }
>> +
>
>This fix should be done in mas_store_root(), which will probably reduce
>or remove your lengthy comment.
>
>mas_root_expand() should... expand the root, and this isn't what is
>happening now.
>
Right, will move it.
Thanks
>> node = mas_pop_node(mas);
>> pivots = ma_pivots(node, type);
>> slots = ma_slots(node, type);
>> --
>> 2.34.1
>>
--
Wei Yang
Help you, Help me
