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Date:   Fri, 22 May 2020 12:45:44 +0100
From:   Chris Down <chris@chrisdown.name>
To:     Naresh Kamboju <naresh.kamboju@linaro.org>
Cc:     Yafang Shao <laoar.shao@gmail.com>,
        Michal Hocko <mhocko@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Roman Gushchin <guro@fb.com>, linux-mm <linux-mm@kvack.org>,
        Cgroups <cgroups@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        lkft-triage@lists.linaro.org
Subject: Re: [PATCH v3 2/2] mm, memcg: Decouple e{low,min} state mutations
 from protection checks
Message-ID: <20200522114544.GA1112005@chrisdown.name>
References: <20200505084127.12923-1-laoar.shao@gmail.com>
 <20200505084127.12923-3-laoar.shao@gmail.com>
 <CA+G9fYseWc_7yq0M5Onju_HxbFid6DbuuaEFf-KUpqfxdF-QTg@mail.gmail.com>
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Naresh Kamboju writes:
>This patch is causing oom-killer while running mkfs -t ext4 on i386 kernel
>running on x86_64 machine version linux-next 5.7.0-rc6-next-20200521.

I think I see what's wrong here -- if we bail out early, memory.e{min,low} 
might be uninitialised.

Does this patch fix it, by any chance?

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d3b23c57bed4..aa902b9cbb79 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5046,6 +5046,9 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
  			memory_cgrp_subsys.broken_hierarchy = true;
  	}
  
+	memcg->memory.emin = 0;
+	memcg->memory.elow = 0;
+
  	/* The following stuff does not apply to the root */
  	if (!parent) {
  #ifdef CONFIG_MEMCG_KMEM
-- 
2.26.2