diff --git a/mm/slab.h b/mm/slab.h index a3a967d7d7c2..bf51a8d254cf 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -181,10 +181,6 @@ bool __kmem_cache_alloc_bulk(struct kmem_cache *, gfp_t, size_t, void **); list_for_each_entry(iter, &(root)->memcg_params.list, \ memcg_params.list) -#define for_each_memcg_cache_safe(iter, tmp, root) \ - list_for_each_entry_safe(iter, tmp, &(root)->memcg_params.list, \ - memcg_params.list) - static inline bool is_root_cache(struct kmem_cache *s) { return s->memcg_params.is_root_cache; @@ -265,8 +261,6 @@ extern void slab_init_memcg_params(struct kmem_cache *); #define for_each_memcg_cache(iter, root) \ for ((void)(iter), (void)(root); 0; ) -#define for_each_memcg_cache_safe(iter, tmp, root) \ - for ((void)(iter), (void)(tmp), (void)(root); 0; ) static inline bool is_root_cache(struct kmem_cache *s) { diff --git a/mm/slab_common.c b/mm/slab_common.c index c8d2ed7f8330..ab1f20e303e4 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -461,10 +461,6 @@ static int shutdown_cache(struct kmem_cache *s, if (s->flags & SLAB_DESTROY_BY_RCU) *need_rcu_barrier = true; -#ifdef CONFIG_MEMCG_KMEM - if (!is_root_cache(s)) - list_del(&s->memcg_params.list); -#endif list_move(&s->list, release); return 0; } @@ -597,6 +593,18 @@ void memcg_deactivate_kmem_caches(struct mem_cgroup *memcg) put_online_cpus(); } +static int __shutdown_memcg_cache(struct kmem_cache *s, + struct list_head *release, bool *need_rcu_barrier) +{ + BUG_ON(is_root_cache(s)); + + if (shutdown_cache(s, release, need_rcu_barrier)) + return -EBUSY; + + list_del(&s->memcg_params.list); + return 0; +} + void memcg_destroy_kmem_caches(struct mem_cgroup *memcg) { LIST_HEAD(release); @@ -614,7 +622,7 @@ void memcg_destroy_kmem_caches(struct mem_cgroup *memcg) * The cgroup is about to be freed and therefore has no charges * left. Hence, all its caches must be empty by now. */ - BUG_ON(shutdown_cache(s, &release, &need_rcu_barrier)); + BUG_ON(__shutdown_memcg_cache(s, &release, &need_rcu_barrier)); } mutex_unlock(&slab_mutex); @@ -623,6 +631,68 @@ void memcg_destroy_kmem_caches(struct mem_cgroup *memcg) release_caches(&release, need_rcu_barrier); } + +static int shutdown_memcg_caches(struct kmem_cache *s, + struct list_head *release, bool *need_rcu_barrier) +{ + struct memcg_cache_array *arr; + struct kmem_cache *c, *c2; + LIST_HEAD(busy); + int i; + + BUG_ON(!is_root_cache(s)); + + /* + * First, shutdown active caches, i.e. caches that belong to online + * memory cgroups. + */ + arr = rcu_dereference_protected(s->memcg_params.memcg_caches, + lockdep_is_held(&slab_mutex)); + for_each_memcg_cache_index(i) { + c = arr->entries[i]; + if (!c) + continue; + if (__shutdown_memcg_cache(c, release, need_rcu_barrier)) + /* + * The cache still has objects. Move it to a temporary + * list so as not to try to destroy it for a second + * time while iterating over inactive caches below. + */ + list_move(&c->memcg_params.list, &busy); + else + /* + * The cache is empty and will be destroyed soon. Clear + * the pointer to it in the memcg_caches array so that + * it will never be accessed even if the root cache + * stays alive. + */ + arr->entries[i] = NULL; + } + + /* + * Second, shutdown all caches left from memory cgroups that are now + * offline. + */ + list_for_each_entry_safe(c, c2, &s->memcg_params.list, + memcg_params.list) + __shutdown_memcg_cache(c, release, need_rcu_barrier); + + list_splice(&busy, &s->memcg_params.list); + + /* + * A cache being destroyed must be empty. In particular, this means + * that all per memcg caches attached to it must be empty too. + */ + if (!list_empty(&s->memcg_params.list)) + return -EBUSY; + return 0; +} +#else +static inline int shutdown_memcg_caches(struct kmem_cache *s, + struct list_head *release, bool *need_rcu_barrier) +{ + return 0; +} #endif /* CONFIG_MEMCG_KMEM */ void slab_kmem_cache_release(struct kmem_cache *s) @@ -634,16 +704,13 @@ void slab_kmem_cache_release(struct kmem_cache *s) void kmem_cache_destroy(struct kmem_cache *s) { - struct kmem_cache *c, *c2; LIST_HEAD(release); bool need_rcu_barrier = false; - bool busy = false; + int err; if (unlikely(!s)) return; - BUG_ON(!is_root_cache(s)); - get_online_cpus(); get_online_mems(); @@ -653,12 +720,8 @@ void kmem_cache_destroy(struct kmem_cache *s) if (s->refcount) goto out_unlock; - for_each_memcg_cache_safe(c, c2, s) { - if (shutdown_cache(c, &release, &need_rcu_barrier)) - busy = true; - } - - if (!busy) + err = shutdown_memcg_caches(s, &release, &need_rcu_barrier); + if (!err) shutdown_cache(s, &release, &need_rcu_barrier); out_unlock: