Re: [PATCH net-next 02/13] sk_buff: add skb extension infrastructure

[Eric Dumazet]

On 12/13/2018 03:03 AM, Florian Westphal wrote:
> Eric Dumazet <eric.duma...@gmail.com> wrote:
>>
>>
>> On 12/13/2018 02:39 AM, Florian Westphal wrote:
>>>
>>> Thats whats done in the MPTCP out-of-tree implementation, but I don't
>>> think its needed.
>>>
>>> It could just delete the extension before ->queue_xmit() AFAIU.
>>
>> So, cloning would do an refcount_inc(), and deleting the extension would do 
>> an refcount_dec_and_test() ?
>>
>> That is what I called an extra pair of atomic operations.
> 
> If it replaces 1:1 current mptcp skb->private out-of-tree storage, then
> yes.
> 

One day I will write a book on the number of atomic operations done on a TCP 
sendmsg() system call :/