mm/list_lru: remove list_lru_putback()

Since the only user zswap_lru_putback() has gone, remove
list_lru_putback() too.

Link: https://lkml.kernel.org/r/20240126-zswap-writeback-race-v2-3-b10479847099@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com> 
Cc: Chris Li <chriscli@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/list_lru.h

@@ -168,22 +168,6 @@ static inline unsigned long list_lru_count(struct list_lru *lru)
 void list_lru_isolate(struct list_lru_one *list, struct list_head *item);
 void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
 			   struct list_head *head);
-/**
- * list_lru_putback: undo list_lru_isolate
- * @lru: the lru pointer.
- * @item: the item to put back.
- * @nid: the node id of the sublist to put the item back to.
- * @memcg: the cgroup of the sublist to put the item back to.
- *
- * Put back an isolated item into its original LRU. Note that unlike
- * list_lru_add, this does not increment the node LRU count (as
- * list_lru_isolate does not originally decrement this count).
- *
- * Since we might have dropped the LRU lock in between, recompute list_lru_one
- * from the node's id and memcg.
- */
-void list_lru_putback(struct list_lru *lru, struct list_head *item, int nid,
-		      struct mem_cgroup *memcg);
 
 typedef enum lru_status (*list_lru_walk_cb)(struct list_head *item,
 		struct list_lru_one *list, spinlock_t *lock, void *cb_arg);

mm/list_lru.c

@@ -162,20 +162,6 @@ void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
 }
 EXPORT_SYMBOL_GPL(list_lru_isolate_move);
 
-void list_lru_putback(struct list_lru *lru, struct list_head *item, int nid,
-		      struct mem_cgroup *memcg)
-{
-	struct list_lru_one *list =
-		list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg));
-
-	if (list_empty(item)) {
-		list_add_tail(item, &list->list);
-		if (!list->nr_items++)
-			set_shrinker_bit(memcg, nid, lru_shrinker_id(lru));
-	}
-}
-EXPORT_SYMBOL_GPL(list_lru_putback);
-
 unsigned long list_lru_count_one(struct list_lru *lru,
 				 int nid, struct mem_cgroup *memcg)
 {

mm/zswap.c

@@ -410,7 +410,7 @@ static void zswap_lru_add(struct list_lru *list_lru, struct zswap_entry *entry)
 	 * 2. list_lru_add() is called after memcg->kmemcg_id is updated. The
 	 *    new entry will be added directly to memcg's parent's list_lru.
 	 *
-	 * Similar reasoning holds for list_lru_del() and list_lru_putback().
+	 * Similar reasoning holds for list_lru_del().
 	 */
 	rcu_read_lock();
 	memcg = mem_cgroup_from_entry(entry);