[PATCH v3 1/7] mm: list_lru: lock_list_lru_of_memcg() cannot return NULL if !skip_empty

[Johannes Weiner <hannes@cmpxchg.org>]

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@kernel.org>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 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 26463ae29c64..d96fd50fc9af 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);
 		/* Set shrinker bit if the first element was added */
@@ -203,9 +201,8 @@ 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--;
-- 
2.53.0