[PATCH v5 2/9] mm: list_lru: lock_list_lru_of_memcg() cannot return NULL if !skip_empty

[Johannes Weiner]

skip_empty is only for the shrinker to abort and skip a list that's
empty or whose cgroup is being deleted.

For list additions and deletions, the cgroup hierarchy is walked
upwards until a valid list_lru head is found, or it will fall back to
the node list. Acquiring the lock won't fail. Remove the NULL checks
in those callers.

Reviewed-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>
Acked-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@xxxxxxxxxx>
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Liam R. Howlett (Oracle) <liam@xxxxxxxxxxxxx>
---
 mm/list_lru.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/mm/list_lru.c b/mm/list_lru.c
index 45d1b97737ea..77999ed78fa5 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -165,8 +165,6 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item, int nid,
 	struct list_lru_one *l;
 
 	l = lock_list_lru_of_memcg(lru, nid, &memcg, false, false);
-	if (!l)
-		return false;
 	if (list_empty(item)) {
 		list_add_tail(item, &l->list);
 		/*
@@ -208,9 +206,8 @@ bool list_lru_del(struct list_lru *lru, struct list_head *item, int nid,
 {
 	struct list_lru_node *nlru = &lru->node[nid];
 	struct list_lru_one *l;
+
 	l = lock_list_lru_of_memcg(lru, nid, &memcg, false, false);
-	if (!l)
-		return false;
 	if (!list_empty(item)) {
 		list_del_init(item);
 		l->nr_items--;
-- 
2.54.0