netdev - Re: TUN problems (regression?)

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Message-Id: <20121221.131531.837406858012872917.davem@davemloft.net>
Date:	Fri, 21 Dec 2012 13:15:31 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	jasowang@...hat.com
Cc:	shemminger@...tta.com, eric.dumazet@...il.com, pmoore@...hat.com,
	netdev@...r.kernel.org
Subject: Re: TUN problems (regression?)

From: Jason Wang <jasowang@...hat.com>
Date: Fri, 21 Dec 2012 11:32:43 +0800

> On 12/21/2012 07:50 AM, Stephen Hemminger wrote:
>> On Thu, 20 Dec 2012 15:38:17 -0800
>> Eric Dumazet <eric.dumazet@...il.com> wrote:
>>
>>> On Thu, 2012-12-20 at 18:16 -0500, Paul Moore wrote:
>>>> [CC'ing netdev in case this is a known problem I just missed ...]
>>>>
>>>> Hi Jason,
>>>>
>>>> I started doing some more testing with the multiqueue TUN changes and I ran 
>>>> into a problem when running tunctl: running it once w/o arguments works as 
>>>> expected, but running it a second time results in failure and a 
>>>> kmem_cache_sanity_check() failure.  The problem appears to be very repeatable 
>>>> on my test VM and happens independent of the LSM/SELinux fixup patches.
>>>>
>>>> Have you seen this before?
>>>>
>>> Obviously code in tun_flow_init() is wrong...
>>>
>>> static int tun_flow_init(struct tun_struct *tun)
>>> {
>>>         int i;
>>>
>>>         tun->flow_cache = kmem_cache_create("tun_flow_cache",
>>>                                             sizeof(struct tun_flow_entry), 0, 0,
>>>                                             NULL);
>>>         if (!tun->flow_cache)
>>>                 return -ENOMEM;
>>> ...
>>> }
>>>
>>>
>>> I have no idea why we would need a kmem_cache per tun_struct,
>>> and why we even need a kmem_cache.
>> Normally flow malloc/free should be good enough.
>> It might make sense to use private kmem_cache if doing hlist_nulls.
>>
>>
>> Acked-by: Stephen Hemminger <shemminger@...tta.com>
> 
> Should be at least a global cache, I thought I can get some speed-up by
> using kmem_cache.
> 
> Acked-by: Jason Wang <jasowang@...hat.com>

Applied.
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