[PATCH v5 3/6] zswap: make shrinking memcg-aware (fix)

[Nhat Pham <nphamcs@gmail.com>]

Rename get_mem_cgroup_from_entry() to mem_cgroup_from_entry() and use
the zswap_pools_lock for next_shrink update.

Suggested-by: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
---
 mm/zswap.c | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 2654b0d214cc..f1998dbd3519 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -174,7 +174,6 @@ struct zswap_pool {
 	struct hlist_node node;
 	char tfm_name[CRYPTO_MAX_ALG_NAME];
 	struct list_lru list_lru;
-	spinlock_t next_shrink_lock;
 	struct mem_cgroup *next_shrink;
 };
 
@@ -292,7 +291,7 @@ static void zswap_update_total_size(void)
 }
 
 /* should be called under RCU */
-static inline struct mem_cgroup *get_mem_cgroup_from_entry(struct zswap_entry *entry)
+static inline struct mem_cgroup *mem_cgroup_from_entry(struct zswap_entry *entry)
 {
 	return entry->objcg ? obj_cgroup_memcg(entry->objcg) : NULL;
 }
@@ -309,11 +308,9 @@ void zswap_memcg_offline_cleanup(struct mem_cgroup *memcg)
 	/* lock out zswap pools list modification */
 	spin_lock(&zswap_pools_lock);
 	list_for_each_entry(pool, &zswap_pools, list) {
-		spin_lock(&pool->next_shrink_lock);
 		if (pool->next_shrink == memcg)
 			pool->next_shrink =
 				mem_cgroup_iter(NULL, pool->next_shrink, NULL, true);
-		spin_unlock(&pool->next_shrink_lock);
 	}
 	spin_unlock(&zswap_pools_lock);
 }
@@ -360,7 +357,7 @@ static void zswap_lru_add(struct list_lru *list_lru, struct zswap_entry *entry)
 	 * Similar reasoning holds for list_lru_del() and list_lru_putback().
 	 */
 	rcu_read_lock();
-	memcg = get_mem_cgroup_from_entry(entry);
+	memcg = mem_cgroup_from_entry(entry);
 	/* will always succeed */
 	list_lru_add(list_lru, &entry->lru, nid, memcg);
 	rcu_read_unlock();
@@ -372,7 +369,7 @@ static void zswap_lru_del(struct list_lru *list_lru, struct zswap_entry *entry)
 	struct mem_cgroup *memcg;
 
 	rcu_read_lock();
-	memcg = get_mem_cgroup_from_entry(entry);
+	memcg = mem_cgroup_from_entry(entry);
 	/* will always succeed */
 	list_lru_del(list_lru, &entry->lru, nid, memcg);
 	rcu_read_unlock();
@@ -386,7 +383,7 @@ static void zswap_lru_putback(struct list_lru *list_lru,
 	struct mem_cgroup *memcg;
 
 	rcu_read_lock();
-	memcg = get_mem_cgroup_from_entry(entry);
+	memcg = mem_cgroup_from_entry(entry);
 	spin_lock(lock);
 	/* we cannot use list_lru_add here, because it increments node's lru count */
 	list_lru_putback(list_lru, &entry->lru, nid, memcg);
@@ -806,13 +803,13 @@ static void shrink_worker(struct work_struct *w)
 
 	/* global reclaim will select cgroup in a round-robin fashion. */
 	do {
-		spin_lock(&pool->next_shrink_lock);
+		spin_lock(&zswap_pools_lock);
 		memcg = pool->next_shrink =
 			mem_cgroup_iter(NULL, pool->next_shrink, NULL, true);
 
 		/* full round trip */
 		if (!memcg) {
-			spin_unlock(&pool->next_shrink_lock);
+			spin_unlock(&zswap_pools_lock);
 			if (++failures == MAX_RECLAIM_RETRIES)
 				break;
 
@@ -824,7 +821,7 @@ static void shrink_worker(struct work_struct *w)
 		 * original reference is dropped by the zswap offlining callback.
 		 */
 		css_get(&memcg->css);
-		spin_unlock(&pool->next_shrink_lock);
+		spin_unlock(&zswap_pools_lock);
 
 		ret = shrink_memcg(memcg);
 		mem_cgroup_put(memcg);
@@ -898,7 +895,6 @@ static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
 	INIT_WORK(&pool->shrink_work, shrink_worker);
 
 	zswap_pool_debug("created", pool);
-	spin_lock_init(&pool->next_shrink_lock);
 
 	return pool;
 
@@ -963,10 +959,10 @@ static void zswap_pool_destroy(struct zswap_pool *pool)
 	free_percpu(pool->acomp_ctx);
 	list_lru_destroy(&pool->list_lru);
 
-	spin_lock(&pool->next_shrink_lock);
+	spin_lock(&zswap_pools_lock);
 	mem_cgroup_put(pool->next_shrink);
 	pool->next_shrink = NULL;
-	spin_unlock(&pool->next_shrink_lock);
+	spin_unlock(&zswap_pools_lock);
 
 	for (i = 0; i < ZSWAP_NR_ZPOOLS; i++)
 		zpool_destroy_pool(pool->zpools[i]);
-- 
2.34.1