memcg: notify about global mem_cgroup_id space depletion

memcg: notify about global mem_cgroup_id space depletion

Currently, the host owner is not informed about the exhaustion of the
global mem_cgroup_id space.  When this happens, systemd cannot start a new
service and receives a unique -ENOSPC error code.  However, this can
happen inside this container, persist in the log file of the local
container, and may not be noticed by the host owner if he did not try to
start any new services.

Link: https://lkml.kernel.org/r/97bed1fd-f230-c2ea-1cb6-8230825a9a64@openvz.org
Signed-off-by: Vasily Averin <vvs@openvz.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>