在 2026/9/4 03:11, Waiman Long 写道:
> On 9/2/26 6:26 AM, Guopeng Zhang wrote:
>> From: Guopeng Zhang <[email protected]>
>>
>> compute_partition_effective_cpumask() checks whether each valid child
>> partition remains covered by the parent exclusive CPU mask and whether it
>> would consume all remaining CPUs of a populated parent.
>>
>> Factor these two checks into child_partition_error() so the same rules can
>> be reused when evaluating a proposed parent configuration. This is a
>> preparatory refactoring with no intended functional change.
>>
>> Signed-off-by: Guopeng Zhang <[email protected]>
>> ---
>> kernel/cgroup/cpuset.c | 38 +++++++++++++++++++++++++++++---------
>> 1 file changed, 29 insertions(+), 9 deletions(-)
>>
>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>> index 8f24171b6055..6994dc75d940 100644
>> --- a/kernel/cgroup/cpuset.c
>> +++ b/kernel/cgroup/cpuset.c
>> @@ -2085,6 +2085,26 @@ static int update_parent_effective_cpumask(struct
>> cpuset *cs, int cmd,
>> return 0;
>> }
>> +/*
>> + * Return the error that will invalidate a child partition under a proposed
>> + * parent partition configuration.
>> + */
>> +static enum prs_errcode
>> +child_partition_error(struct cpuset *child,
>> + const struct cpumask *partition_cpus,
>> + const struct cpumask *remaining_cpus,
>> + bool parent_populated)
>> +{
>> + if (!cpumask_subset(child->effective_xcpus, partition_cpus))
>> + return PERR_INVCPUS;
>> +
>> + if (parent_populated &&
>> + cpumask_subset(remaining_cpus, child->effective_xcpus))
>> + return PERR_NOCPUS;
>> +
>> + return PERR_NONE;
>> +}
>> +
>> /**
>> * compute_partition_effective_cpumask - compute effective_cpus for
>> partition
>> * @cs: partition root cpuset
>> @@ -2121,6 +2141,8 @@ static void compute_partition_effective_cpumask(struct
>> cpuset *cs,
>> rcu_read_lock();
>> cpuset_for_each_child(child, css, cs) {
>> + enum prs_errcode child_err;
>> +
>> if (!is_partition_valid(child))
>> continue;
>> @@ -2129,15 +2151,13 @@ static void
>> compute_partition_effective_cpumask(struct cpuset *cs,
>> * partition root.
>> */
>> WARN_ON_ONCE(is_remote_partition(child));
>> - WRITE_ONCE(child->prs_err, 0);
>> - if (!cpumask_subset(child->effective_xcpus,
>> - cs->effective_xcpus))
>
> Looking at the patch again, I now see that the current code is incorrect. It
> should be "if (!cpumask_subset(child->effective_xcpus, new_ecpus))" So you
> only need to pass the "parent_excpus" (for instance) to the new helper
> instead of passing two.
>
Longman, thanks for your review.
Yes, you are right that using `cs->effective_xcpus` here is incorrect.
In v1, I had a change for this issue, and based on your comment [1], I moved it
to another fix. I also followed Ridong's suggestion to split the original
17-patch series into smaller series. I split it into three parts locally, and
the current series is the second part, so this fix is not included here.
I plan to address this in the third series, together with the CPU ownership and
isolation accounting issues following child partition invalidation.
In that series, the two masks have different meanings: the newly computed
unfiltered exclusive mask, including offline CPUs, is used for the child
containment check, while the active CPU mask remaining after child ownership is
accounted for is used for the `PERR_NOCPUS` check. So I would prefer to keep
the two-mask interface here and clarify their meanings with comments.
Does this approach make sense to you?
[1] https://lore.kernel.org/all/[email protected]/
Thanks,
Guopeng
