netdev - Re: ICMP packets - ll_temac with Microblaze

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Date:	Wed, 21 Dec 2011 12:10:28 +0100
From:	Michal Simek <monstr@...str.eu>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	David Miller <davem@...emloft.net>,
	John Williams <john.williams@...alogix.com>,
	netdev@...r.kernel.org
Subject: Re: ICMP packets - ll_temac with Microblaze

Eric Dumazet wrote:
> Le mercredi 21 décembre 2011 à 11:45 +0100, Eric Dumazet a écrit :
>> Le mercredi 21 décembre 2011 à 11:41 +0100, Michal Simek a écrit :
>>
>>> yes, page size is 4k.
>>>
>>> Here is the log for allocation - origin size for MTU 9000 is 0x2420(9248) and size after
>>> overhead is 0x3f40(16192)
>>>
>>> kmalloc_node_track_caller size 00002420, SKB_WITH_OVERHEAD(ksize(data)) 00003f40
>>> skb->head     c7870000
>>> skb->data     c7870000
>>> skb->tail     c7870000
>>> skb->truesize 000040c0
>>> skb->end      c7873f40
>>>
>> So basically truesize is bigger than previous kernel, and you hit a
>> socket limit.  (RCVBUF ?)
>>
>> truesize is more correct, so we uncover prior bugs.
>>
>> We should allow at least one packet, regardless of its size :(
>>
>>
> 
> I would try the following patch :
> 
> diff --git a/include/net/sock.h b/include/net/sock.h
> index bf6b9fd..21bb3b5 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -662,12 +662,14 @@ static inline void __sk_add_backlog(struct sock *sk, struct sk_buff *skb)
>  
>  /*
>   * Take into account size of receive queue and backlog queue
> + * Do not take into account this skb truesize,
> + * to allow even a single big packet to come.
>   */
>  static inline bool sk_rcvqueues_full(const struct sock *sk, const struct sk_buff *skb)
>  {
>  	unsigned int qsize = sk->sk_backlog.len + atomic_read(&sk->sk_rmem_alloc);
>  
> -	return qsize + skb->truesize > sk->sk_rcvbuf;
> +	return qsize > sk->sk_rcvbuf;
>  }
>  
>  /* The per-socket spinlock must be held here. */
> 

It doesn't fix the problem. Do you want to add some printk to code?

Michal



-- 
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian
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