From: dingtianhong <dingtianhong@huawei.com>
Date: Fri, 13 Dec 2013 02:20:02 +0000 (+0800)
Subject: bonding: rebuild the lock use for bond_activebackup_arp_mon()
X-Git-Tag: v3.14-rc1~94^2~495^2~5
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=eb9fa4b0199f62df3d174d32b4bd534df8ba4533;p=pandora-kernel.git

bonding: rebuild the lock use for bond_activebackup_arp_mon()

The bond_activebackup_arp_mon() use the bond lock for read to
protect the slave list, it is no effect, and the RTNL is only
called for bond_ab_arp_commit() and peer notify, for the performance
better, use RCU to replace with the bond lock, to the bond slave
list need to called in RCU, add a new bond_first_slave_rcu()
to get the first slave in RCU protection.

In bond_ab_arp_probe(), the bond->current_arp_slave may changd
if bond release slave, just like:

        bond_ab_arp_probe()                     bond_release()
        cpu 0                                   cpu 1
        ...
        if (bond->current_arp_slave...)         ...
        ...                             bond->current_arp_slave = NULl
        bond->current_arp_slave->dev->name      ...

So the current_arp_slave need to dereference in the section.

Suggested-by: Nikolay Aleksandrov <nikolay@redhat.com>
Suggested-by: Jay Vosburgh <fubar@us.ibm.com>
Suggested-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

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