Re: [PATCH 3/3] cgroup: use nodes_and() output where appropriate

[Chen Ridong]

On 2026/1/15 6:33, Waiman Long wrote:
> On 1/14/26 12:22 PM, Yury Norov wrote:
>> Now that nodes_and() returns true if the result nodemask is not empty,
>> drop useless nodes_intersects() in guarantee_online_mems() and
>> nodes_empty() in update_nodemasks_hier(), which both are O(N).
>>
>> Signed-off-by: Yury Norov <ynorov@xxxxxxxxxx>
>> ---
>>   kernel/cgroup/cpuset.c | 7 +++----
>>   1 file changed, 3 insertions(+), 4 deletions(-)
>>
>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>> index 3e8cc34d8d50..e962efbb300d 100644
>> --- a/kernel/cgroup/cpuset.c
>> +++ b/kernel/cgroup/cpuset.c
>> @@ -456,9 +456,8 @@ static void guarantee_active_cpus(struct task_struct *tsk,
>>    */
>>   static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)
>>   {
>> -    while (!nodes_intersects(cs->effective_mems, node_states[N_MEMORY]))
>> +    while (!nodes_and(*pmask, cs->effective_mems, node_states[N_MEMORY]))
>>           cs = parent_cs(cs);
>> -    nodes_and(*pmask, cs->effective_mems, node_states[N_MEMORY]);
>>   }
>>     /**
>> @@ -2862,13 +2861,13 @@ static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
>>       cpuset_for_each_descendant_pre(cp, pos_css, cs) {
>>           struct cpuset *parent = parent_cs(cp);
>>   -        nodes_and(*new_mems, cp->mems_allowed, parent->effective_mems);
>> +        bool has_mems = nodes_and(*new_mems, cp->mems_allowed, parent->effective_mems);
>>             /*
>>            * If it becomes empty, inherit the effective mask of the
>>            * parent, which is guaranteed to have some MEMs.
>>            */
>> -        if (is_in_v2_mode() && nodes_empty(*new_mems))
>> +        if (is_in_v2_mode() && !has_mems)
>>               *new_mems = parent->effective_mems;
>>             /* Skip the whole subtree if the nodemask remains the same. */
> Reviewed-by: Waiman Long <longman@xxxxxxxxxx>
> 

Reviewed-by: Chen Ridong <chenridong@xxxxxxxxxxxxxxx>

-- 
Best regards,
Ridong