mm: memcontrol: zap memcg_kmem_online helper

As kmem accounting is now either enabled for all cgroups or disabled
system-wide, there's no point in having memcg_kmem_online() helper -
instead one can use memcg_kmem_enabled() and mem_cgroup_online(), as
shrink_slab() now does.

There are only two places left where this helper is used -
__memcg_kmem_charge() and memcg_create_kmem_cache().  The former can
only be called if memcg_kmem_enabled() returned true.  Since the cgroup
it operates on is online, mem_cgroup_is_root() check will be enough.

memcg_create_kmem_cache() can't use mem_cgroup_online() helper instead
of memcg_kmem_online(), because it relies on the fact that in
memcg_offline_kmem() memcg->kmem_state is changed before
memcg_deactivate_kmem_caches() is called, but there we can just
open-code the check.

Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 28d1b1e9d4fb..341bf86d26c2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2346,7 +2346,7 @@ int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order)
         int ret = 0;
 
         memcg = get_mem_cgroup_from_mm(current->mm);
-        if (memcg_kmem_online(memcg))
+        if (!mem_cgroup_is_root(memcg))
                 ret = __memcg_kmem_charge_memcg(page, gfp, order, memcg);
         css_put(&memcg->css);
         return ret;