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

[Nhat Pham]

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 <yosryah...@google.com>
Signed-off-by: Nhat Pham <npha...@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