linux-kernel - [PATCH -next RFC 04/16] cpuset: factor out partition

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Message-Id: <20250928071306.3797436-5-chenridong@huaweicloud.com>
Date: Sun, 28 Sep 2025 07:12:54 +0000
From: Chen Ridong <chenridong@...weicloud.com>
To: longman@...hat.com,
	tj@...nel.org,
	hannes@...xchg.org,
	mkoutny@...e.com
Cc: cgups@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	lujialin4@...wei.com,
	chenridong@...wei.com
Subject: [PATCH -next RFC 04/16] cpuset: factor out partition_disable() function

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

Extract the core partition disablement logic into a dedicated
partition_disable() function. This refactoring centralizes updates to key
cpuset data structures including remote_sibling, effective_xcpus,
partition_root_state, and prs_err.

The function handles the complete partition disablement workflow:
- Removing exclusive CPUs via partition_xcpus_del()
- Cleaning up remote sibling relationships
- Recomputing effective exclusive CPUs mask
- Updating partition state and error status
- Triggering required scheduler domain rebuilds

This creates a symmetric interface with partition_enable() and establishes
a foundation for future local partition support while maintaining existing
remote partition behavior.

Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
 kernel/cgroup/cpuset.c | 49 +++++++++++++++++++++++++++---------------
 1 file changed, 32 insertions(+), 17 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 43ce62f4959c..1944410ae872 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1558,6 +1558,35 @@ static void partition_enable(struct cpuset *cs, struct cpuset *parent,
 	cpuset_force_rebuild();
 }
 
+/**
+ * partition_disable - Disable partition root state for a cpuset
+ * @cs: The cpuset to disable partition for
+ * @parent: Parent cpuset of @cs, NULL for remote parent
+ * @new_prs: New partition root state (should be non-positive)
+ * @prs_err: Error code to set if disabling due to validation failure
+ */
+static void partition_disable(struct cpuset *cs, struct cpuset *parent,
+				    int new_prs, enum prs_errcode prs_err)
+{
+	bool isolcpus_updated;
+
+	lockdep_assert_held(&cpuset_mutex);
+	WARN_ON_ONCE(new_prs > 0);
+	WARN_ON_ONCE(!cpuset_v2());
+
+	spin_lock_irq(&callback_lock);
+	list_del_init(&cs->remote_sibling);
+	/* disable a partition should only delete exclusive cpus */
+	isolcpus_updated = partition_xcpus_del(cs->partition_root_state,
+						parent, cs->effective_xcpus);
+	/* effective_xcpus may need to be changed */
+	compute_excpus(cs, cs->effective_xcpus);
+	partition_state_update(cs, new_prs, prs_err);
+	spin_unlock_irq(&callback_lock);
+	update_unbound_workqueue_cpumask(isolcpus_updated);
+	cpuset_force_rebuild();
+}
+
 /*
  * remote_partition_enable - Enable current cpuset as a remote partition root
  * @cs: the cpuset to update
@@ -1613,27 +1642,13 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
  */
 static void remote_partition_disable(struct cpuset *cs, struct tmpmasks *tmp)
 {
-	bool isolcpus_updated;
+	int new_prs;
 
 	WARN_ON_ONCE(!is_remote_partition(cs));
 	WARN_ON_ONCE(!cpumask_subset(cs->effective_xcpus, subpartitions_cpus));
 
-	spin_lock_irq(&callback_lock);
-	list_del_init(&cs->remote_sibling);
-	isolcpus_updated = partition_xcpus_del(cs->partition_root_state,
-					       NULL, cs->effective_xcpus);
-	if (cs->prs_err)
-		cs->partition_root_state = -cs->partition_root_state;
-	else
-		cs->partition_root_state = PRS_MEMBER;
-
-	/* effective_xcpus may need to be changed */
-	compute_excpus(cs, cs->effective_xcpus);
-	reset_partition_data(cs);
-	spin_unlock_irq(&callback_lock);
-	update_unbound_workqueue_cpumask(isolcpus_updated);
-	cpuset_force_rebuild();
-
+	new_prs = cs->prs_err ? -cs->partition_root_state : PRS_MEMBER;
+	partition_disable(cs, NULL, new_prs, cs->prs_err);
 	/*
 	 * Propagate changes in top_cpuset's effective_cpus down the hierarchy.
 	 */
-- 
2.34.1