sched/fair: Allow disabling sched_balance_newidle with sched_relax_domain_level

Change relax_domain_level checks so that it would be possible
to include or exclude all domains from newidle balancing.

This matches the behavior described in the documentation:

  -1   no request. use system default or follow request of others.
   0   no search.
   1   search siblings (hyperthreads in a core).

"2" enables levels 0 and 1, level_max excludes the last (level_max)
level, and level_max+1 includes all levels.

Fixes: 1d3504fc ("sched, cpuset: customize sched domains, core")
Signed-off-by: Vitalii Bursov <vitaly@bursov.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lore.kernel.org/r/bd6de28e80073c79466ec6401cdeae78f0d4423d.1714488502.git.vitaly@bursov.com

kernel/cgroup/cpuset.c

@@ -2948,7 +2948,7 @@ bool current_cpuset_is_being_rebound(void)
 static int update_relax_domain_level(struct cpuset *cs, s64 val)
 {
 #ifdef CONFIG_SMP
-	if (val < -1 || val >= sched_domain_level_max)
+	if (val < -1 || val > sched_domain_level_max + 1)
 		return -EINVAL;
 #endif
 

kernel/sched/topology.c

@@ -1475,7 +1475,7 @@ static void set_domain_attribute(struct sched_domain *sd,
 	} else
 		request = attr->relax_domain_level;
 
-	if (sd->level > request) {
+	if (sd->level >= request) {
 		/* Turn off idle balance on this domain: */
 		sd->flags &= ~(SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
 	}