netdev - Re: [PATCH v2 -next] 6LoWPAN: fix skb

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Date:	Thu, 1 Sep 2011 16:34:54 +0400
From:	Alexander Smirnov <alex.bluesman.smirnov@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	davem@...emloft.net, dbaryshkov@...il.com, slapin@...fans.org,
	linux-zigbee-devel@...ts.sourceforge.net, netdev@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH v2 -next] 6LoWPAN: fix skb_copy call

Hi Eric,

hmm, I think you are right.

First 6LoWPAN implementation was developed as a part of MAC layer and
code was based on this layer approach. But now 6lowpan is
MAC-independent, it's just a netif_rx hook and looks like I missed
this moment during migration.

sorry for confusion.

With best regards,
Alexander

2011/9/1 Eric Dumazet <eric.dumazet@...il.com>:
> Le jeudi 01 septembre 2011 à 16:54 +0400, Alexander Smirnov a écrit :
>> This patch fixes 2 issues in lowpan_skb_deliver function:
>> 1. Check for return status of skb_copy call;
>> 2. Use skb_copy with proper GFP flag depending on context.
>>
>> Signed-off-by: Alexander Smirnov <alex.bluesman.smirnov@...il.com>
>> ---
>>  net/ieee802154/6lowpan.c |   18 +++++++++++++++---
>>  1 files changed, 15 insertions(+), 3 deletions(-)
>>
>> diff --git a/net/ieee802154/6lowpan.c b/net/ieee802154/6lowpan.c
>> index cf304cc..16100be 100644
>> --- a/net/ieee802154/6lowpan.c
>> +++ b/net/ieee802154/6lowpan.c
>> @@ -477,9 +477,15 @@ static int lowpan_skb_deliver(struct sk_buff *skb, struct ipv6hdr *hdr)
>>       struct sk_buff *new;
>>       struct lowpan_dev_record *entry;
>>       int stat = NET_RX_SUCCESS;
>> +     gfp_t mask;
>>
>> -     new = skb_copy_expand(skb, sizeof(struct ipv6hdr), skb_tailroom(skb),
>> -                                                             GFP_KERNEL);
>> +     if (in_interrupt())
>> +             mask = GFP_ATOMIC;
>> +     else
>> +             mask = GFP_KERNEL;
>
> I am not sure to understand if lowpan_skb_deliver() can be called in
> pure process context. I feel we are in softirq handler or we have
> disabled BH, so GFP_ATOMIC is the only choice.
>
> If you are unsure, you could use following helper :
>
>        mask = gfp_any();
>
>> +
>> +     new = skb_copy_expand(skb, sizeof(struct ipv6hdr),
>> +                                     skb_tailroom(skb), mask);
>>       kfree_skb(skb);
>>
>
>
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