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Date:   Sat, 25 Jun 2022 17:04:27 +0300
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From:   Vasily Averin <vvs@openvz.org>
Subject: [PATCH RFC] memcg: notify about global mem_cgroup_id space depletion
To:     Shakeel Butt <shakeelb@google.com>,
        =?UTF-8?Q?Michal_Koutn=c3=bd?= <mkoutny@suse.com>,
        Michal Hocko <mhocko@suse.com>
Cc:     kernel@openvz.org, linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Vlastimil Babka <vbabka@suse.cz>,
        Muchun Song <songmuchun@bytedance.com>, cgroups@vger.kernel.org
References: <YrXDV7uPpmDigh3G@dhcp22.suse.cz>
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Currently host owner is not informed about the exhaustion of the
global mem_cgroup_id space. When this happens, systemd cannot
start a new service, but nothing points to the real cause of
this failure.

Signed-off-by: Vasily Averin <vvs@openvz.org>
---
 mm/memcontrol.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d4c606a06bcd..5229321636f2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5317,6 +5317,7 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
 				 1, MEM_CGROUP_ID_MAX + 1, GFP_KERNEL);
 	if (memcg->id.id < 0) {
 		error = memcg->id.id;
+		pr_notice_ratelimited("mem_cgroup_id space is exhausted\n");
 		goto fail;
 	}
 
-- 
2.36.1