Re: [PATCH -mm v2 3/8] memcg: mark caches that belong to offline memcgs as dead

Joonsoo Kim
2014-06-10T07:44:51Z

On Fri, Jun 06, 2014 at 05:22:40PM +0400, Vladimir Davydov wrote:
> This will be used by the next patches.
>
> Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
> Acked-by: Christoph Lameter <cl@linux.com>
> ---
> include/linux/slab.h | 2 ++
> mm/memcontrol.c | 1 +
> mm/slab.h | 10 ++++++++++
> 3 files changed, 13 insertions(+)
>
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index d9716fdc8211..d99d5212b815 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -527,6 +527,7 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
> * @list: list_head for the list of all caches in this memcg
> * @root_cache: pointer to the global, root cache, this cache was derived from
> * @refcnt: reference counter
> + * @dead: set to true when owner memcg is turned offline
> * @unregister_work: worker to destroy the cache
> */
> struct memcg_cache_params {
> @@ -541,6 +542,7 @@ struct memcg_cache_params {
> struct list_head list;
> struct kmem_cache *root_cache;
> atomic_long_t refcnt;
> + bool dead;
> struct work_struct unregister_work;
> };
> };
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 886b5b414958..ed42fd1105a5 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3294,6 +3294,7 @@ static void memcg_unregister_all_caches(struct mem_cgroup *memcg)
> mutex_lock(&memcg_slab_mutex);
> list_for_each_entry_safe(params, tmp, &memcg->memcg_slab_caches, list) {
> cachep = memcg_params_to_cache(params);
> + cachep->memcg_params->dead = true;

I guess that this needs smp_wmb() and memcg_cache_dead() needs
smp_rmb(), since we could call memcg_cache_dead() without holding any locks.

Thanks.