ipvs: Fix estimator kthreads preferred affinity

JIRA: https://issues.redhat.com/browse/RHEL-115582
Upstream Status: commit c0a23bb

commit c0a23bb
Author: Frederic Weisbecker <frederic@kernel.org>
Date:   Tue Jul 29 14:26:11 2025 +0200

    ipvs: Fix estimator kthreads preferred affinity

    The estimator kthreads' affinity are defined by sysctl overwritten
    preferences and applied through a plain call to the scheduler's affinity
    API.

    However since the introduction of managed kthreads preferred affinity,
    such a practice shortcuts the kthreads core code which eventually
    overwrites the target to the default unbound affinity.

    Fix this with using the appropriate kthread's API.

    Fixes: d1a8919 ("kthread: Default affine kthread to its preferred NUMA node")
    Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
    Acked-by: Julian Anastasov <ja@ssi.bg>
    Signed-off-by: Florian Westphal <fw@strlen.de>

Signed-off-by: Florian Westphal <fwestpha@redhat.com>

Author: fw-strlen

include/net/ip_vs.h

@@ -1163,6 +1163,14 @@ static inline const struct cpumask *sysctl_est_cpulist(struct netns_ipvs *ipvs)
 		return housekeeping_cpumask(HK_TYPE_KTHREAD);
 }
 
+static inline const struct cpumask *sysctl_est_preferred_cpulist(struct netns_ipvs *ipvs)
+{
+	if (ipvs->est_cpulist_valid)
+		return ipvs->sysctl_est_cpulist;
+	else
+		return NULL;
+}
+
 static inline int sysctl_est_nice(struct netns_ipvs *ipvs)
 {
 	return ipvs->sysctl_est_nice;
@@ -1270,6 +1278,11 @@ static inline const struct cpumask *sysctl_est_cpulist(struct netns_ipvs *ipvs)
 	return housekeeping_cpumask(HK_TYPE_KTHREAD);
 }
 
+static inline const struct cpumask *sysctl_est_preferred_cpulist(struct netns_ipvs *ipvs)
+{
+	return NULL;
+}
+
 static inline int sysctl_est_nice(struct netns_ipvs *ipvs)
 {
 	return IPVS_EST_NICE;

kernel/kthread.c

@@ -893,6 +893,7 @@ int kthread_affine_preferred(struct task_struct *p, const struct cpumask *mask)
 
 	return ret;
 }
+EXPORT_SYMBOL_GPL(kthread_affine_preferred);
 
 /*
  * Re-affine kthreads according to their preferences

net/netfilter/ipvs/ip_vs_est.c

@@ -265,7 +265,8 @@ int ip_vs_est_kthread_start(struct netns_ipvs *ipvs,
 	}
 
 	set_user_nice(kd->task, sysctl_est_nice(ipvs));
-	set_cpus_allowed_ptr(kd->task, sysctl_est_cpulist(ipvs));
+	if (sysctl_est_preferred_cpulist(ipvs))
+		kthread_affine_preferred(kd->task, sysctl_est_preferred_cpulist(ipvs));
 
 	pr_info("starting estimator thread %d...\n", kd->id);
 	wake_up_process(kd->task);