linux-kernel - Re: [PATCH net-next v9 09/13] net: introduce the skb_copy_to_va

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Message-ID: <d2e4d25d-33d8-22d9-c5e0-16be802ad39a@huawei.com>
Date: Wed, 3 Jul 2024 20:36:16 +0800
From: Yunsheng Lin <linyunsheng@...wei.com>
To: Alexander H Duyck <alexander.duyck@...il.com>, <davem@...emloft.net>,
	<kuba@...nel.org>, <pabeni@...hat.com>
CC: <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Eric Dumazet
	<edumazet@...gle.com>
Subject: Re: [PATCH net-next v9 09/13] net: introduce the
 skb_copy_to_va_nocache() helper

On 2024/7/2 23:52, Alexander H Duyck wrote:
> On Tue, 2024-06-25 at 21:52 +0800, Yunsheng Lin wrote:
>> introduce the skb_copy_to_va_nocache() helper to avoid
>> calling virt_to_page() and skb_copy_to_page_nocache().
>>
>> CC: Alexander Duyck <alexander.duyck@...il.com>
>> Signed-off-by: Yunsheng Lin <linyunsheng@...wei.com>
>> ---
>>  include/net/sock.h | 15 +++++++++++++++
>>  1 file changed, 15 insertions(+)
>>
>> diff --git a/include/net/sock.h b/include/net/sock.h
>> index cce23ac4d514..7ad235465485 100644
>> --- a/include/net/sock.h
>> +++ b/include/net/sock.h
>> @@ -2201,6 +2201,21 @@ static inline int skb_copy_to_page_nocache(struct sock *sk, struct iov_iter *fro
>>  	return 0;
>>  }
>>  
>> +static inline int skb_copy_to_va_nocache(struct sock *sk, struct iov_iter *from,
>> +					 struct sk_buff *skb, char *va, int copy)
>> +{
>> +	int err;
>> +
>> +	err = skb_do_copy_data_nocache(sk, skb, from, va, copy, skb->len);
>> +	if (err)
>> +		return err;
>> +
>> +	skb_len_add(skb, copy);
>> +	sk_wmem_queued_add(sk, copy);
>> +	sk_mem_charge(sk, copy);
>> +	return 0;
>> +}
>> +
>>  /**
>>   * sk_wmem_alloc_get - returns write allocations
>>   * @sk: socket
> 
> One minor nit. Rather than duplicate skb_copy_to_page_nocache you would
> be better served to implement this one before it, and then just update
> skb_copy_to_page_nocache to be:
> 	return skb_copy_to_va_nocache(sk, from, skb,
> 				      page_address(page) + off, copy);
> 
> We can save ourselves at least a few lines of code that way and it
> creates one spot to do any changes.

Looking at more closely, it seems we may be able to just rename
skb_copy_to_page_nocache() to skb_copy_to_va_nocache() as there
is no caller for skb_copy_to_page_nocache() after this patchset.

> 				
> .
>