Re: [PATCH v2 1/2] cgroup/cpuset: reset DL migration state on can_attach() failure

[Waiman Long <longman@redhat.com>]

On 5/7/26 6:33 AM, Guopeng Zhang wrote:
> cpuset_can_attach() accumulates temporary SCHED_DEADLINE migration
> state in the destination cpuset while walking the taskset.
>
> If a later task_can_attach() or security_task_setscheduler() check
> fails, cgroup_migrate_execute() treats cpuset as the failing subsystem
> and does not call cpuset_cancel_attach() for it. The partially
> accumulated state is then left behind and can be consumed by a later
> attach, corrupting cpuset DL task accounting and pending DL bandwidth
> accounting.
>
> Reset the pending DL migration state before returning from those
> per-task failure paths.
>
> Fixes: 2ef269ef1ac0 ("cgroup/cpuset: Free DL BW in case can_attach() fails")
> Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
> ---
>   kernel/cgroup/cpuset.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index e3a081a07c6d..ae41736399a1 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -3029,12 +3029,12 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
>   	cgroup_taskset_for_each(task, css, tset) {
>   		ret = task_can_attach(task);
>   		if (ret)
> -			goto out_unlock;
> +			goto out_reset_dl_data;
>   
>   		if (setsched_check) {
>   			ret = security_task_setscheduler(task);
>   			if (ret)
> -				goto out_unlock;
> +				goto out_reset_dl_data;
>   		}
>   
>   		if (dl_task(task)) {
> @@ -3070,6 +3070,10 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
>   	 * changes which zero cpus/mems_allowed.
>   	 */
>   	cs->attach_in_progress++;
> +	goto out_unlock;
> +
> +out_reset_dl_data:
> +	reset_migrate_dl_data(cs);
>   out_unlock:
>   	mutex_unlock(&cpuset_mutex);
>   	return ret;

I would prefer the likely success path be a straight line instead of 
doing a goto. IOW, move out_reset_dl_data below return. Other than that, 
this patch looks good to me.

Cheers,
Longman