memcg: don't check mm in __memcg_kmem_{get_cache,newpage_charge}

We already assured the current task has mm in memcg_kmem_should_charge,
no need to double check.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -2856,7 +2856,7 @@ struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep,
 	VM_BUG_ON(!cachep->memcg_params);
 	VM_BUG_ON(!cachep->memcg_params->is_root_cache);
 
-	if (!current->mm || current->memcg_kmem_skip_account)
+	if (current->memcg_kmem_skip_account)
 		return cachep;
 
 	rcu_read_lock();
@@ -2942,7 +2942,7 @@ __memcg_kmem_newpage_charge(gfp_t gfp, struct mem_cgroup **_memcg, int order)
 	 * allocations are extremely rare but can happen, for instance, for the
 	 * cache arrays. We bring this test here.
 	 */
-	if (!current->mm || current->memcg_kmem_skip_account)
+	if (current->memcg_kmem_skip_account)
 		return true;
 
 	memcg = get_mem_cgroup_from_mm(current->mm);