From cf2b8fbf1d2f7ba07999e97685563c94483d33d6 Mon Sep 17 00:00:00 2001
From: Vladimir Davydov <vdavydov@parallels.com>
Date: Thu, 9 Oct 2014 15:28:59 -0700
Subject: [PATCH] memcg: zap memcg_can_account_kmem

memcg_can_account_kmem() returns true iff

    !mem_cgroup_disabled() && !mem_cgroup_is_root(memcg) &&
                                   memcg_kmem_is_active(memcg);

To begin with the !mem_cgroup_is_root(memcg) check is useless, because one
can't enable kmem accounting for the root cgroup (mem_cgroup_write()
returns EINVAL on an attempt to set the limit on the root cgroup).

Furthermore, the !mem_cgroup_disabled() check also seems to be redundant.
The point is memcg_can_account_kmem() is called from three places:
mem_cgroup_salbinfo_read(), __memcg_kmem_get_cache(), and
__memcg_kmem_newpage_charge().  The latter two functions are only invoked
if memcg_kmem_enabled() returns true, which implies that the memory cgroup
subsystem is enabled.  And mem_cgroup_slabinfo_read() shows the output of
memory.kmem.slabinfo, which won't exist if the memory cgroup is completely
disabled.

So let's substitute all the calls to memcg_can_account_kmem() with plain
memcg_kmem_is_active(), and kill the former.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: 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>
---
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