cgroup: make sure memcg margin is 0 when over limit
For the memcg sock code, we'll need to register allocations
that are temporarily over limit. Let's make sure that margin
is 0 in this case.
I am keeping this as a separate patch, so that if any weirdness
interaction appears in the future, we can now exactly what caused
it.
Suggested by Johannes Weiner
Signed-off-by: Glauber Costa <glommer@parallels.com>
CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
CC: Johannes Weiner <hannes@cmpxchg.org>
CC: Michal Hocko <mhocko@suse.cz>
CC: Tejun Heo <tj@kernel.org>
CC: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
index c9d625c..d06d014 100644
--- a/include/linux/res_counter.h
+++ b/include/linux/res_counter.h
@@ -142,7 +142,10 @@
unsigned long flags;
spin_lock_irqsave(&cnt->lock, flags);
- margin = cnt->limit - cnt->usage;
+ if (cnt->limit > cnt->usage)
+ margin = cnt->limit - cnt->usage;
+ else
+ margin = 0;
spin_unlock_irqrestore(&cnt->lock, flags);
return margin;
}