mm: memcontrol: refactor memcg_reparent_objcgs()

Refactor the memcg_reparent_objcgs() to facilitate subsequent reparenting
LRU folios here.

Link: https://lore.kernel.org/2e5696db1993e593a51004c1dacedbc261689629.1772711148.git.zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Cc: Allen Pais <apais@linux.microsoft.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Chen Ridong <chenridong@huawei.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Imran Khan <imran.f.khan@oracle.com>
Cc: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yosry Ahmed <yosry@kernel.org>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 24 insertions, 5 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0d4eaaea2b54..e43ca8da8daf 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -208,15 +208,12 @@ static struct obj_cgroup *obj_cgroup_alloc(void)
 	return objcg;
 }
 
-static void memcg_reparent_objcgs(struct mem_cgroup *memcg)
+static inline struct obj_cgroup *__memcg_reparent_objcgs(struct mem_cgroup *memcg,
+							 struct mem_cgroup *parent)
 {
 	struct obj_cgroup *objcg, *iter;
-	struct mem_cgroup *parent = parent_mem_cgroup(memcg);
 
 	objcg = rcu_replace_pointer(memcg->objcg, NULL, true);
-
-	spin_lock_irq(&objcg_lock);
-
 	/* 1) Ready to reparent active objcg. */
 	list_add(&objcg->list, &memcg->objcg_list);
 	/* 2) Reparent active objcg and already reparented objcgs to parent. */
@@ -225,7 +222,29 @@ static void memcg_reparent_objcgs(struct mem_cgroup *memcg)
 	/* 3) Move already reparented objcgs to the parent's list */
 	list_splice(&memcg->objcg_list, &parent->objcg_list);
 
+	return objcg;
+}
+
+static inline void reparent_locks(struct mem_cgroup *memcg, struct mem_cgroup *parent)
+{
+	spin_lock_irq(&objcg_lock);
+}
+
+static inline void reparent_unlocks(struct mem_cgroup *memcg, struct mem_cgroup *parent)
+{
 	spin_unlock_irq(&objcg_lock);
+}
+
+static void memcg_reparent_objcgs(struct mem_cgroup *memcg)
+{
+	struct obj_cgroup *objcg;
+	struct mem_cgroup *parent = parent_mem_cgroup(memcg);
+
+	reparent_locks(memcg, parent);
+
+	objcg = __memcg_reparent_objcgs(memcg, parent);
+
+	reparent_unlocks(memcg, parent);
 
 	percpu_ref_kill(&objcg->refcnt);
 }