linux-kernel - [PATCH -next RFC 09/11] cpuset: refactor partition_cpus

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Message-Id: <20250828125631.1978176-10-chenridong@huaweicloud.com>
Date: Thu, 28 Aug 2025 12:56:29 +0000
From: Chen Ridong <chenridong@...weicloud.com>
To: longman@...hat.com,
	tj@...nel.org,
	hannes@...xchg.org,
	mkoutny@...e.com
Cc: cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	lujialin4@...wei.com,
	chenridong@...wei.com
Subject: [PATCH -next RFC 09/11] cpuset: refactor partition_cpus_change

From: Chen Ridong <chenridong@...wei.com>

Refactor the partition_cpus_change function to handle both regular CPU
set updates and exclusive CPU modifications, either of which may trigger
partition state changes. This generalized function will also be utilized
for exclusive CPU updates in subsequent patches.

Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
 kernel/cgroup/cpuset.c | 59 ++++++++++++++++++++++++++----------------
 1 file changed, 36 insertions(+), 23 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 75ad18ab40ae..e3eb87a33b12 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -2447,6 +2447,41 @@ static int acpus_validate_change(struct cpuset *cs, struct cpuset *trialcs,
 	return retval;
 }
 
+/**
+ * partition_cpus_change - Handle partition state changes due to CPU mask updates
+ * @cs: The target cpuset being modified
+ * @trialcs: The trial cpuset containing proposed configuration changes
+ * @tmp: Temporary masks for intermediate calculations
+ *
+ * This function handles partition state transitions triggered by CPU mask changes.
+ * CPU modifications may cause a partition to be disabled or require state updates.
+ */
+static void partition_cpus_change(struct cpuset *cs, struct cpuset *trialcs,
+					struct tmpmasks *tmp)
+{
+	if (cs_is_member(cs))
+		return;
+
+	invalidate_cs_partition(trialcs);
+	if (trialcs->prs_err)
+		cs->prs_err = trialcs->prs_err;
+
+	if (is_remote_partition(cs)) {
+		if (trialcs->prs_err)
+			remote_partition_disable(cs, tmp);
+		else
+			remote_cpus_update(cs, trialcs->exclusive_cpus,
+					   trialcs->effective_xcpus, tmp);
+	} else {
+		if (trialcs->prs_err)
+			update_parent_effective_cpumask(cs, partcmd_invalidate,
+							NULL, tmp);
+		else
+			update_parent_effective_cpumask(cs, partcmd_update,
+							trialcs->effective_xcpus, tmp);
+	}
+}
+
 /**
  * update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it
  * @cs: the cpuset to consider
@@ -2483,29 +2518,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
 	 */
 	force = !cpumask_equal(cs->effective_xcpus, trialcs->effective_xcpus);
 
-	invalidate_cs_partition(trialcs);
-	if (trialcs->prs_err)
-		cs->prs_err = trialcs->prs_err;
-
-	if (is_partition_valid(cs) ||
-	   (is_partition_invalid(cs) && !trialcs->prs_err)) {
-		struct cpumask *xcpus = trialcs->effective_xcpus;
-
-		if (cpumask_empty(xcpus) && is_partition_invalid(cs))
-			xcpus = trialcs->cpus_allowed;
-
-		/*
-		 * Call remote_cpus_update() to handle valid remote partition
-		 */
-		if (is_remote_partition(cs))
-			remote_cpus_update(cs, NULL, xcpus, &tmp);
-		else if (trialcs->prs_err)
-			update_parent_effective_cpumask(cs, partcmd_invalidate,
-							NULL, &tmp);
-		else
-			update_parent_effective_cpumask(cs, partcmd_update,
-							xcpus, &tmp);
-	}
+	partition_cpus_change(cs, trialcs, &tmp);
 
 	spin_lock_irq(&callback_lock);
 	cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
-- 
2.34.1