linux-kernel - [PATCH -next 09/21] cpuset: introduce local_partition

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Message-Id: <20251117024627.1128037-10-chenridong@huaweicloud.com>
Date: Mon, 17 Nov 2025 02:46:15 +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 09/21] cpuset: introduce local_partition_enable()

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

The partition_enable() function introduced in the previous patch can be
reused to enable local partitions.

The local_partition_enable() function is introduced, which factors out the
local partition enablement logic from update_parent_effective_cpumask().
After passing local partition validation checks, it delegates to
partition_enable() to complete the partition setup.

This refactoring creates a clear separation between local and remote
partition operations while maintaining code reuse through the shared
partition_enable() infrastructure.

Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
 kernel/cgroup/cpuset.c | 86 ++++++++++++++++++++++++------------------
 1 file changed, 50 insertions(+), 36 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 392b01f95e62..3c1e8431c234 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1897,6 +1897,52 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus,
 	remote_partition_disable(cs, tmp);
 }
 
+/**
+ * local_partition_enable - Enable local partition for a cpuset
+ * @cs: Target cpuset to become a local partition root
+ * @new_prs: New partition root state to apply
+ * @tmp: Temporary masks for CPU calculations
+ *
+ * Return: 0 on success, error code on failure
+ */
+static int local_partition_enable(struct cpuset *cs,
+				int new_prs, struct tmpmasks *tmp)
+{
+	struct cpuset *parent = parent_cs(cs);
+	enum prs_errcode err;
+
+	lockdep_assert_held(&cpuset_mutex);
+	WARN_ON_ONCE(is_remote_partition(cs));	/* For local partition only */
+
+	/*
+	 * The parent must be a partition root.
+	 * The new cpumask, if present, or the current cpus_allowed must
+	 * not be empty.
+	 */
+	if (!is_partition_valid(parent)) {
+		return is_partition_invalid(parent)
+			? PERR_INVPARENT : PERR_NOTPART;
+	}
+
+	/*
+	 * Need to call compute_excpus() in case
+	 * exclusive_cpus not set. Sibling conflict should only happen
+	 * if exclusive_cpus isn't set.
+	 */
+	if (compute_excpus(cs, tmp->new_cpus))
+		WARN_ON_ONCE(!cpumask_empty(cs->exclusive_cpus));
+
+	err = validate_partition(cs, new_prs, tmp->new_cpus, tmp->new_cpus, NULL);
+	if (err)
+		return err;
+
+	partition_enable(cs, parent, new_prs, tmp->new_cpus);
+
+	cpuset_update_tasks_cpumask(parent, tmp->addmask);
+	update_sibling_cpumasks(parent, cs, tmp);
+	return 0;
+}
+
 /**
  * update_parent_effective_cpumask - update effective_cpus mask of parent cpuset
  * @cs:      The cpuset that requests change in partition root state
@@ -1987,35 +2033,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
 
 	nocpu = tasks_nocpu_error(parent, cs, xcpus);
 
-	if ((cmd == partcmd_enable) || (cmd == partcmd_enablei)) {
-		/*
-		 * Need to call compute_excpus() in case
-		 * exclusive_cpus not set. Sibling conflict should only happen
-		 * if exclusive_cpus isn't set.
-		 */
-		xcpus = tmp->delmask;
-		if (compute_excpus(cs, xcpus))
-			WARN_ON_ONCE(!cpumask_empty(cs->exclusive_cpus));
-		new_prs = (cmd == partcmd_enable) ? PRS_ROOT : PRS_ISOLATED;
-
-		part_error = validate_partition(cs, new_prs, xcpus, xcpus, NULL);
-		if (part_error)
-			return part_error;
-
-		/*
-		 * This function will only be called when all the preliminary
-		 * checks have passed. At this point, the following condition
-		 * should hold.
-		 *
-		 * (cs->effective_xcpus & cpu_active_mask) ⊆ parent->effective_cpus
-		 *
-		 * Warn if it is not the case.
-		 */
-		cpumask_and(tmp->new_cpus, xcpus, cpu_active_mask);
-		WARN_ON_ONCE(!cpumask_subset(tmp->new_cpus, parent->effective_cpus));
-
-		deleting = true;
-	} else if (cmd == partcmd_disable) {
+	if (cmd == partcmd_disable) {
 		/*
 		 * May need to add cpus back to parent's effective_cpus
 		 * (and maybe removed from subpartitions_cpus/isolated_cpus)
@@ -3147,14 +3165,10 @@ static int update_prstate(struct cpuset *cs, int new_prs)
 		 * If parent is valid partition, enable local partiion.
 		 * Otherwise, enable a remote partition.
 		 */
-		if (is_partition_valid(parent)) {
-			enum partition_cmd cmd = (new_prs == PRS_ROOT)
-					       ? partcmd_enable : partcmd_enablei;
-
-			err = update_parent_effective_cpumask(cs, cmd, NULL, &tmpmask);
-		} else {
+		if (is_partition_valid(parent))
+			err = local_partition_enable(cs, new_prs, &tmpmask);
+		else
 			err = remote_partition_enable(cs, new_prs, &tmpmask);
-		}
 	} else if (old_prs && new_prs) {
 		/*
 		 * A change in load balance state only, no change in cpumasks.
-- 
2.34.1