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-rw-r--r--mm/memcontrol.c15
-rw-r--r--mm/slab.h16
2 files changed, 23 insertions, 8 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 80197e544764..216659d4441a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3178,18 +3178,17 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
if (num_groups > memcg_limited_groups_array_size) {
int i;
+ struct memcg_cache_params *new_params;
ssize_t size = memcg_caches_array_size(num_groups);
size *= sizeof(void *);
size += offsetof(struct memcg_cache_params, memcg_caches);
- s->memcg_params = kzalloc(size, GFP_KERNEL);
- if (!s->memcg_params) {
- s->memcg_params = cur_params;
+ new_params = kzalloc(size, GFP_KERNEL);
+ if (!new_params)
return -ENOMEM;
- }
- s->memcg_params->is_root_cache = true;
+ new_params->is_root_cache = true;
/*
* There is the chance it will be bigger than
@@ -3203,7 +3202,7 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
for (i = 0; i < memcg_limited_groups_array_size; i++) {
if (!cur_params->memcg_caches[i])
continue;
- s->memcg_params->memcg_caches[i] =
+ new_params->memcg_caches[i] =
cur_params->memcg_caches[i];
}
@@ -3216,7 +3215,9 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
* bigger than the others. And all updates will reset this
* anyway.
*/
- kfree(cur_params);
+ rcu_assign_pointer(s->memcg_params, new_params);
+ if (cur_params)
+ kfree_rcu(cur_params, rcu_head);
}
return 0;
}
diff --git a/mm/slab.h b/mm/slab.h
index 72d1f9df71bd..8184a7cde272 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -160,14 +160,28 @@ static inline const char *cache_name(struct kmem_cache *s)
return s->name;
}
+/*
+ * Note, we protect with RCU only the memcg_caches array, not per-memcg caches.
+ * That said the caller must assure the memcg's cache won't go away. Since once
+ * created a memcg's cache is destroyed only along with the root cache, it is
+ * true if we are going to allocate from the cache or hold a reference to the
+ * root cache by other means. Otherwise, we should hold either the slab_mutex
+ * or the memcg's slab_caches_mutex while calling this function and accessing
+ * the returned value.
+ */
static inline struct kmem_cache *
cache_from_memcg_idx(struct kmem_cache *s, int idx)
{
struct kmem_cache *cachep;
+ struct memcg_cache_params *params;
if (!s->memcg_params)
return NULL;
- cachep = s->memcg_params->memcg_caches[idx];
+
+ rcu_read_lock();
+ params = rcu_dereference(s->memcg_params);
+ cachep = params->memcg_caches[idx];
+ rcu_read_unlock();
/*
* Make sure we will access the up-to-date value. The code updating