From e9897071350bd9d94a56b5b6f79c85b1a98fc7e7 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Fri, 7 Jun 2013 08:48:57 -0700
Subject: [PATCH] igmp: hash a hash table to speedup ip_check_mc_rcu()

After IP route cache removal, multicast applications using
a lot of multicast addresses hit a O(N) behavior in ip_check_mc_rcu()

Add a per in_device hash table to get faster lookup.

This hash table is created only if the number of items in mc_list is
above 4.

Reported-by: Shawn Bohrer <sbohrer@rgmadvisors.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Shawn Bohrer <sbohrer@rgmadvisors.com>
Reviewed-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Reading git-format-patch failed