Re: [PATCH cgroup/for-next v2 1/5] cgroup/cpuset: Add a cpuset_reserve_dl_bw() helper

[Aaron Tomlin]

On Sat, May 16, 2026 at 12:24:44AM -0400, Waiman Long wrote:
> Extract the DL bandwidth allocation code in cpuset_attach() to a new
> cpuset_reserve_dl_bw() helper to simplify code.
> 
> No functional change is expected.
> 
> Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
> ---
>  kernel/cgroup/cpuset.c | 53 ++++++++++++++++++++++++------------------
>  1 file changed, 30 insertions(+), 23 deletions(-)
> 
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index bcefc9f50ac5..7cae47829013 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -2980,6 +2980,25 @@ static int cpuset_can_attach_check(struct cpuset *cs)
>  	return 0;
>  }
>  
> +static int cpuset_reserve_dl_bw(struct cpuset *cs)
> +{
> +	int cpu, ret;
> +
> +	if (!cs->sum_migrate_dl_bw)
> +		return 0;
> +
> +	cpu = cpumask_any_and(cpu_active_mask, cs->effective_cpus);
> +	if (unlikely(cpu >= nr_cpu_ids))
> +		return -EINVAL;
> +
> +	ret = dl_bw_alloc(cpu, cs->sum_migrate_dl_bw);
> +	if (ret)
> +		return ret;
> +
> +	cs->dl_bw_cpu = cpu;
> +	return 0;
> +}
> +
>  static void reset_migrate_dl_data(struct cpuset *cs)
>  {
>  	cs->nr_migrate_dl_tasks = 0;
> @@ -2994,7 +3013,7 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
>  	struct cpuset *cs, *oldcs;
>  	struct task_struct *task;
>  	bool setsched_check;
> -	int cpu, ret;
> +	int ret;
>  
>  	/* used later by cpuset_attach() */
>  	cpuset_attach_old_cs = task_cs(cgroup_taskset_first(tset, &css));
> @@ -3050,31 +3069,19 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
>  		}
>  	}
>  
> -	if (!cs->sum_migrate_dl_bw)
> -		goto out_success;
> -
> -	cpu = cpumask_any_and(cpu_active_mask, cs->effective_cpus);
> -	if (unlikely(cpu >= nr_cpu_ids)) {
> -		ret = -EINVAL;
> -		goto out_unlock;
> -	}
> -
> -	ret = dl_bw_alloc(cpu, cs->sum_migrate_dl_bw);
> -	if (ret)
> -		goto out_unlock;
> -
> -	cs->dl_bw_cpu = cpu;
> -
> -out_success:
> -	/*
> -	 * Mark attach is in progress.  This makes validate_change() fail
> -	 * changes which zero cpus/mems_allowed.
> -	 */
> -	cs->attach_in_progress++;
> +	ret = cpuset_reserve_dl_bw(cs);
>  
>  out_unlock:
> -	if (ret)
> +	if (ret) {
>  		reset_migrate_dl_data(cs);
> +	} else {
> +		/*
> +		 * Mark attach is in progress.  This makes validate_change() fail
> +		 * changes which zero cpus/mems_allowed.
> +		 */
> +		cs->attach_in_progress++;
> +	}
> +
>  	mutex_unlock(&cpuset_mutex);
>  	return ret;
>  }
> -- 
> 2.54.0
> 

Reviewed-by: Aaron Tomlin <atomlin@xxxxxxxxxxx>

-- 
Aaron Tomlin