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Subject: Re: [PATCH net-next 11/12] net: hns3: do not allocate linear data for
 fraglist skb
To:     Jakub Kicinski <jakub.kicinski@netronome.com>
CC:     <davem@davemloft.net>, <netdev@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <salil.mehta@huawei.com>,
        <yisen.zhuang@huawei.com>, <linuxarm@huawei.com>,
        Yunsheng Lin <linyunsheng@huawei.com>
References: <1571210231-29154-1-git-send-email-tanhuazhong@huawei.com>
 <1571210231-29154-12-git-send-email-tanhuazhong@huawei.com>
 <20191016101817.725b6d28@cakuba.netronome.com>
From:   tanhuazhong <tanhuazhong@huawei.com>
Message-ID: <2bf7e500-66e0-1b24-f940-5f8c4952038a@huawei.com>
Date:   Thu, 17 Oct 2019 08:54:28 +0800
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On 2019/10/17 1:18, Jakub Kicinski wrote:
> On Wed, 16 Oct 2019 15:17:10 +0800, Huazhong Tan wrote:
>> From: Yunsheng Lin <linyunsheng@huawei.com>
>>
>> Currently, napi_alloc_skb() is used to allocate skb for fraglist
>> when the head skb is not enough to hold the remaining data, and
>> the remaining data is added to the frags part of the fraglist skb,
>> leaving the linear part unused.
>>
>> So this patch passes length of 0 to allocate fraglist skb with
>> zero size of linear data.
>>
>> Fixes: 81ae0e0491f3 ("net: hns3: Add skb chain when num of RX buf exceeds MAX_SKB_FRAGS")
>> Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
>> Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
> 
> Is this really a fix? I just wastes memory, right?

It is a minor optimizations. This fix tag is a mistake.
Thanks.

> 
>> diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
>> index 6172eb2..14111af 100644
>> --- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
>> +++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
>> @@ -2866,8 +2866,7 @@ static int hns3_add_frag(struct hns3_enet_ring *ring, struct hns3_desc *desc,
>>   			return -ENXIO;
>>   
>>   		if (unlikely(ring->frag_num >= MAX_SKB_FRAGS)) {
>> -			new_skb = napi_alloc_skb(&ring->tqp_vector->napi,
>> -						 HNS3_RX_HEAD_SIZE);
>> +			new_skb = napi_alloc_skb(&ring->tqp_vector->napi, 0);
>>   			if (unlikely(!new_skb)) {
>>   				hns3_rl_err(ring_to_netdev(ring),
>>   					    "alloc rx fraglist skb fail\n");
> 
> 
> .
>