[PATCH 2/4] cpuset: add early empty cpumask check in partition_xcpus_add/del

[Ridong Chen <ridong.chen@linux.dev>]

From: Chen Ridong <chenridong@huawei.com>

Add a check for an empty cpumask at the start of partition_xcpus_add()
and partition_xcpus_del(). This allows the functions to return early,
avoiding unnecessary computation when there is no work to be done. With
these changes, partition_xcpus_add() and partition_xcpus_del() can be
called even if xcpus is empty. The caller no longer needs to check whether
xcpus is empty, eliminating many conditional statements.

Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Signed-off-by: Ridong Chen <chenridong@xiaomi.com>
---
 kernel/cgroup/cpuset.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index bc16fd1b1c5e..68b82dabbf38 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1315,10 +1315,13 @@ static void partition_xcpus_add(int new_prs, struct cpuset *parent,
 {
 	WARN_ON_ONCE(new_prs < 0);
 	lockdep_assert_held(&callback_lock);
+
+	if (cpumask_empty(xcpus))
+		return;
+
 	if (!parent)
 		parent = &top_cpuset;
 
-
 	if (parent == &top_cpuset)
 		cpumask_or(subpartitions_cpus, subpartitions_cpus, xcpus);
 
@@ -1342,6 +1345,10 @@ static void partition_xcpus_del(int old_prs, struct cpuset *parent,
 {
 	WARN_ON_ONCE(old_prs < 0);
 	lockdep_assert_held(&callback_lock);
+
+	if (cpumask_empty(xcpus))
+		return;
+
 	if (!parent)
 		parent = &top_cpuset;
 
-- 
2.34.1