diff options
| -rw-r--r-- | include/linux/slab.h | 9 | ||||
| -rw-r--r-- | mm/memcontrol.c | 15 | ||||
| -rw-r--r-- | mm/slab.h | 16 |
3 files changed, 30 insertions, 10 deletions
diff --git a/include/linux/slab.h b/include/linux/slab.h index 1e2f4fe12773..a060142aa5f5 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -513,7 +513,9 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node) * * Both the root cache and the child caches will have it. For the root cache, * this will hold a dynamically allocated array large enough to hold - * information about the currently limited memcgs in the system. + * information about the currently limited memcgs in the system. To allow the + * array to be accessed without taking any locks, on relocation we free the old + * version only after a grace period. * * Child caches will hold extra metadata needed for its operation. Fields are: * @@ -528,7 +530,10 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node) struct memcg_cache_params { bool is_root_cache; union { - struct kmem_cache *memcg_caches[0]; + struct { + struct rcu_head rcu_head; + struct kmem_cache *memcg_caches[0]; + }; struct { struct mem_cgroup *memcg; struct list_head list; 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 |