netdev - [PATCH v2 net] ipvs: Fix estimator kthreads preferred affinity

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Message-ID: <20250729122611.247368-1-frederic@kernel.org>
Date: Tue, 29 Jul 2025 14:26:11 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Frederic Weisbecker <frederic@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	David Ahern <dsahern@...nel.org>,
	Simon Horman <horms@...ge.net.au>,
	Julian Anastasov <ja@....bg>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Pablo Neira Ayuso <pablo@...filter.org>,
	Jozsef Kadlecsik <kadlec@...filter.org>,
	netdev@...r.kernel.org,
	lvs-devel@...r.kernel.org,
	netfilter-devel@...r.kernel.org,
	coreteam@...filter.org
Subject: [PATCH v2 net] 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: d1a89197589c ("kthread: Default affine kthread to its preferred NUMA node")
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
---
 include/net/ip_vs.h            | 13 +++++++++++++
 kernel/kthread.c               |  1 +
 net/netfilter/ipvs/ip_vs_est.c |  3 ++-
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
index ff406ef4fd4a..29a36709e7f3 100644
--- a/include/net/ip_vs.h
+++ b/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;
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 85e29b250107..adf06196b844 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -899,6 +899,7 @@ int kthread_affine_preferred(struct task_struct *p, const struct cpumask *mask)
 
 	return ret;
 }
+EXPORT_SYMBOL_GPL(kthread_affine_preferred);
 
 static int kthreads_update_affinity(bool force)
 {
diff --git a/net/netfilter/ipvs/ip_vs_est.c b/net/netfilter/ipvs/ip_vs_est.c
index f821ad2e19b3..15049b826732 100644
--- a/net/netfilter/ipvs/ip_vs_est.c
+++ b/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);
-- 
2.48.1