cgroup/cpuset: Remove the unnecessary css_get/put() in cpuset_partition_write()

JIRA: https://issues.redhat.com/browse/RHEL-107751

commit 87eba5b
Author: Waiman Long <longman@redhat.com>
Date:   Wed, 6 Aug 2025 13:24:30 -0400

    cgroup/cpuset: Remove the unnecessary css_get/put() in cpuset_partition_write()

    The css_get/put() calls in cpuset_partition_write() are unnecessary as
    an active reference of the kernfs node will be taken which will prevent
    its removal and guarantee the existence of the css. Only the online
    check is needed.

    Signed-off-by: Waiman Long <longman@redhat.com>
    Reviewed-by: Michal Koutný <mkoutny@suse.com>
    Signed-off-by: Tejun Heo <tj@kernel.org>

Signed-off-by: Waiman Long <longman@redhat.com>

Author: Waiman-Long

kernel/cgroup/cpuset.c

@@ -3358,14 +3358,12 @@ static ssize_t cpuset_partition_write(struct kernfs_open_file *of, char *buf,
 	else
 		return -EINVAL;
 
-	css_get(&cs->css);
 	cpus_read_lock();
 	mutex_lock(&cpuset_mutex);
 	if (is_cpuset_online(cs))
 		retval = update_prstate(cs, val);
 	mutex_unlock(&cpuset_mutex);
 	cpus_read_unlock();
-	css_put(&cs->css);
 	return retval ?: nbytes;
 }