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Date:   Fri, 4 May 2018 13:07:51 +0200
From:   Michal Hocko <mhocko@kernel.org>
To:     "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Kirill Tkhai <ktkhai@virtuozzo.com>, akpm@linux-foundation.org,
        peterz@infradead.org, oleg@redhat.com, viro@zeniv.linux.org.uk,
        mingo@kernel.org, paulmck@linux.vnet.ibm.com,
        keescook@chromium.org, riel@redhat.com, tglx@linutronix.de,
        kirill.shutemov@linux.intel.com, marcos.souza.org@gmail.com,
        hoeun.ryu@gmail.com, pasha.tatashin@oracle.com, gs051095@gmail.com,
        dhowells@redhat.com, rppt@linux.vnet.ibm.com,
        linux-kernel@vger.kernel.org,
        Balbir Singh <balbir@linux.vnet.ibm.com>,
        Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH] memcg: Replace mm->owner with mm->memcg
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I am getting the following for nommu with MEMCG=y randconfig:
kernel/fork.o: In function `mm_init':
fork.c:(.text+0x948): undefined reference to `mm_update_memcg'
kernel/fork.o: In function `mmput':
fork.c:(.text+0x119c): undefined reference to `mm_update_memcg'
make: *** [vmlinux] Error 1

I am sorry but I didn't get to look at it much more but I suspect you
just have to move mm_update_memcg up before mem_cgroup_do_precharge.
-- 
Michal Hocko
SUSE Labs