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Date: Tue, 10 Jul 2012 17:36:50 +0800
From: Gao feng <gaofeng@cn.fujitsu.com>
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To: Eric Dumazet <eric.dumazet@gmail.com>
CC: nhorman@tuxdriver.com, davem@davemloft.net, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, lizefan@huawei.com, tj@kernel.org,
        Eric Dumazet <edumazet@google.com>
Subject: Re: [PATCH] net: cgroup: fix access the unallocated memory in netprio
 cgroup
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于 2012年07月10日 17:15, Eric Dumazet 写道:
> On Tue, 2012-07-10 at 16:53 +0800, Gao feng wrote:
>>> Hi Gao
>>>
>>> Is it still needed to call update_netdev_tables() from write_priomap() ?
>>>
>>
>> Yes, I think it's needed,because read_priomap will show all of the net devices,
>>
>> But we may add the netdev after create a netprio cgroup, so the new added netdev's
>> priomap will not be allocated. if we don't call update_netdev_tables in write_priomap,
>> we may access this unallocated memory.
>>
> 
> I realize my question was not clear.
> 
> If we write in write_priomap() a field of a single netdevice,
> why should we allocate memory for all netdevices on the machine ?
> 
> So the question was : Do we really need to call
> update_netdev_tables(alldevs), instead of extend_netdev_table(dev)
> 
> 

I get it.

You are right,Indeed we only need to call extend_netdev_table
for the netdev witch we want to change.

and I read the commit f5c38208d32412d72b97a4f0d44af0eb39feb20b,
found why we need delay allocation.

I will send a v2 patch.

Thanks!