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mm/memcontrol.c: fix the margin computation in mem_cgroup_margin() 

mem_cgroup_margin() might return (memory.limit - memory_count) when the
memsw.limit is in excess.  This doesn't happen usually because we do not
allow excess on hard limits and (memory.limit <= memsw.limit), but
__GFP_NOFAIL charges can force the charge and cause the excess when no
memory is really swappable (swap is full or no anonymous memory is
left).

[mhocko@suse.com: rewrote changelog]
  Link: http://lkml.kernel.org/r/20160525155122.GK20132@dhcp22.suse.cz
Link: http://lkml.kernel.org/r/1464068266-27736-1-git-send-email-roy.qing.li@gmail.com
Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
Acked-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Li RongQing 2016-05-27 14:27:43 -07:00 committed by Linus Torvalds
parent badbda53e5
commit cbedbac3e6
1 changed files with 2 additions and 0 deletions
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mm/memcontrol.c
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@ -1108,6 +1108,8 @@ static unsigned long mem_cgroup_margin(struct mem_cgroup *memcg)
limit = READ_ONCE(memcg->memsw.limit);
if (count <= limit)
margin = min(margin, limit - count);
else
margin = 0;
}
return margin;