linux-kernel - Re: [PATCH -next RFC 06/16] cpuset: introduce local_partition

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Message-ID: <85e776e6-110e-4c04-88b7-93059db8f74c@redhat.com>
Date: Sun, 19 Oct 2025 22:44:41 -0400
From: Waiman Long <llong@...hat.com>
To: Chen Ridong <chenridong@...weicloud.com>, tj@...nel.org,
 hannes@...xchg.org, mkoutny@...e.com
Cc: cgups@...r.kernel.org, linux-kernel@...r.kernel.org,
 lujialin4@...wei.com, chenridong@...wei.com
Subject: Re: [PATCH -next RFC 06/16] cpuset: introduce
 local_partition_enable()

On 9/28/25 3:12 AM, Chen Ridong wrote:
> From: Chen Ridong <chenridong@...wei.com>
>
> The partition_enable() function introduced in the previous patch can be
> reused to enable local partitions.
>
> First, partition_enable() was enhanced to support local partition enabling
> by properly handling parent's nr_subparts counter and adding notification
> operations.
>
> Then, the local_partition_enable() function is introduced, which factors
> out the local partition enablement logic from
> update_parent_effective_cpumask(). After passing local partition validation
> checks, it delegates to partition_enable() to complete the partition setup.
>
> This refactoring creates a clear separation between local and remote
> partition operations while maintaining code reuse through the shared
> partition_enable() infrastructure.
>
> Signed-off-by: Chen Ridong <chenridong@...wei.com>
> ---
>   kernel/cgroup/cpuset.c | 111 +++++++++++++++++++++++++++--------------
>   1 file changed, 74 insertions(+), 37 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 0e2f95daf459..154992cdfe9a 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -1539,6 +1539,7 @@ static void partition_enable(struct cpuset *cs, struct cpuset *parent,
>   				 int new_prs, struct cpumask *new_excpus)
>   {
>   	bool isolcpus_updated;
> +	int old_prs;
>   
>   	lockdep_assert_held(&cpuset_mutex);
>   	WARN_ON_ONCE(new_prs <= 0);
> @@ -1547,15 +1548,21 @@ static void partition_enable(struct cpuset *cs, struct cpuset *parent,
>   	if (cs->partition_root_state == new_prs)
>   		return;
>   
> +	old_prs = cs->partition_root_state;
>   	spin_lock_irq(&callback_lock);
>   	/* enable partition should only add exclusive cpus */
>   	isolcpus_updated = partition_xcpus_add(new_prs, parent, new_excpus);
> -	list_add(&cs->remote_sibling, &remote_children);
> +	/* enable remote partition */
> +	if (!parent)
> +		list_add(&cs->remote_sibling, &remote_children);
> +	else if (!is_partition_valid(cs))
> +		parent->nr_subparts += 1;
>   	cpumask_copy(cs->effective_xcpus, new_excpus);
>   	partition_state_update(cs, new_prs, PERR_NONE);
>   	spin_unlock_irq(&callback_lock);
>   	update_unbound_workqueue_cpumask(isolcpus_updated);
>   	cpuset_force_rebuild();
> +	notify_partition_change(cs, old_prs);
>   }

As commented in an earlier patch, the partition_enable() chnage should 
be moved there.

Cheers,
Longman