[PATCH 2/7] mm/list_lru: don't pass unnecessary key parameters

[Kairui Song <ryncsn@gmail.com>]

From: Kairui Song <kasong@tencent.com>

When LOCKDEP is not enabled, lock_class_key is an empty struct that
is never used. But the list_lru initialization function still takes
a placeholder pointer as parameter, and the compiler cannot optimize
it because the function is not static and exported.

Remove this parameter and move it inside the list_lru struct. Only
use it when LOCKDEP is enabled. Kernel builds with LOCKDEP will be
slightly larger, while !LOCKDEP builds without it will be slightly
smaller (the common case).

Signed-off-by: Kairui Song <kasong@tencent.com>
---
 include/linux/list_lru.h | 18 +++++++++++++++---
 mm/list_lru.c            |  9 +++++----
 mm/workingset.c          |  4 ++--
 3 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index 792b67ceb631..2e5132905f42 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -56,16 +56,28 @@ struct list_lru {
 	bool			memcg_aware;
 	struct xarray		xa;
 #endif
+#ifdef CONFIG_LOCKDEP
+	struct lock_class_key	*key;
+#endif
 };
 
 void list_lru_destroy(struct list_lru *lru);
 int __list_lru_init(struct list_lru *lru, bool memcg_aware,
-		    struct lock_class_key *key, struct shrinker *shrinker);
+		    struct shrinker *shrinker);
 
 #define list_lru_init(lru)				\
-	__list_lru_init((lru), false, NULL, NULL)
+	__list_lru_init((lru), false, NULL)
 #define list_lru_init_memcg(lru, shrinker)		\
-	__list_lru_init((lru), true, NULL, shrinker)
+	__list_lru_init((lru), true, shrinker)
+
+static inline int list_lru_init_memcg_key(struct list_lru *lru, struct shrinker *shrinker,
+					  struct lock_class_key *key)
+{
+#ifdef CONFIG_LOCKDEP
+	lru->key = key;
+#endif
+	return list_lru_init_memcg(lru, shrinker);
+}
 
 int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru,
 			 gfp_t gfp);
diff --git a/mm/list_lru.c b/mm/list_lru.c
index 3fd64736bc45..264713caa713 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -546,8 +546,7 @@ static void memcg_destroy_list_lru(struct list_lru *lru)
 }
 #endif /* CONFIG_MEMCG_KMEM */
 
-int __list_lru_init(struct list_lru *lru, bool memcg_aware,
-		    struct lock_class_key *key, struct shrinker *shrinker)
+int __list_lru_init(struct list_lru *lru, bool memcg_aware, struct shrinker *shrinker)
 {
 	int i;
 
@@ -567,8 +566,10 @@ int __list_lru_init(struct list_lru *lru, bool memcg_aware,
 
 	for_each_node(i) {
 		spin_lock_init(&lru->node[i].lock);
-		if (key)
-			lockdep_set_class(&lru->node[i].lock, key);
+#ifdef CONFIG_LOCKDEP
+		if (lru->key)
+			lockdep_set_class(&lru->node[i].lock, lru->key);
+#endif
 		init_one_lru(&lru->node[i].lru);
 	}
 
diff --git a/mm/workingset.c b/mm/workingset.c
index c22adb93622a..1801fbe5183c 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -815,8 +815,8 @@ static int __init workingset_init(void)
 	if (!workingset_shadow_shrinker)
 		goto err;
 
-	ret = __list_lru_init(&shadow_nodes, true, &shadow_nodes_key,
-			      workingset_shadow_shrinker);
+	ret = list_lru_init_memcg_key(&shadow_nodes, workingset_shadow_shrinker,
+				      &shadow_nodes_key);
 	if (ret)
 		goto err_list_lru;
 
-- 
2.45.2