From 291487b753b132b382884726f45bc3ffa6ac902e Mon Sep 17 00:00:00 2001
From: Yury Norov <ynorov@nvidia.com>
Date: Wed, 14 Jan 2026 12:22:15 -0500
Subject: [PATCH] cgroup: use nodes_and() output where appropriate
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Now that nodes_and() returns true if the result nodemask is not empty,
drop useless nodes_intersects() in guarantee_online_mems() and
nodes_empty() in update_nodemasks_hier(), which both are O(N).

Link: https://lkml.kernel.org/r/20260114172217.861204-4-ynorov@nvidia.com
Signed-off-by: Yury Norov <ynorov@nvidia.com>
Reviewed-by: Gregory Price <gourry@gourry.net>
Reviewed-by: Joshua Hahn <joshua.hahnjy@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mathew Brost <matthew.brost@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Waiman Long <longman@redhat.com>
Cc: Yury Norov (NVIDIA) <yury.norov@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 kernel/cgroup/cpuset.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index c06e2e96f79dc..99cf37e7d491b 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -453,9 +453,8 @@ static void guarantee_active_cpus(struct task_struct *tsk,
  */
 static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)
 {
-	while (!nodes_intersects(cs->effective_mems, node_states[N_MEMORY]))
+	while (!nodes_and(*pmask, cs->effective_mems, node_states[N_MEMORY]))
 		cs = parent_cs(cs);
-	nodes_and(*pmask, cs->effective_mems, node_states[N_MEMORY]);
 }
 
 /**
@@ -2859,13 +2858,13 @@ static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
 	cpuset_for_each_descendant_pre(cp, pos_css, cs) {
 		struct cpuset *parent = parent_cs(cp);
 
-		nodes_and(*new_mems, cp->mems_allowed, parent->effective_mems);
+		bool has_mems = nodes_and(*new_mems, cp->mems_allowed, parent->effective_mems);
 
 		/*
 		 * If it becomes empty, inherit the effective mask of the
 		 * parent, which is guaranteed to have some MEMs.
 		 */
-		if (is_in_v2_mode() && nodes_empty(*new_mems))
+		if (is_in_v2_mode() && !has_mems)
 			*new_mems = parent->effective_mems;
 
 		/* Skip the whole subtree if the nodemask remains the same. */
-- 
2.47.3