Subject: Re: [RFC v2 3/3] iwlwifi: mvm: transfer the truesize to the last TSO segment

From: Sergei Shtylyov <sergei.shtylyov-M4DtvfQ/[email-masked]>
Date: Wed, 19 Aug 2015 22:16:33 +0300

On 08/19/2015 10:12 PM, Grumbach, Emmanuel wrote:

>>> This allows to release the backpressure on the socket only
>>> when the last segment is released.
>>> Now the truesize looks like this:
>>> if the truesize of the original skb is 65420, all the
>>> segments will have a truesize of 704 (skb itself) and the
>>> last one will have 65420.
>>>
>>> Change-Id: I3c894cf2afc0aedfe7b2a5b992ba41653ff79c0e
>>> Signed-off-by: Emmanuel Grumbach <[email-masked]>
>>> ---
>>>    drivers/net/wireless/iwlwifi/mvm/tx.c | 17 ++++++++++++++++-
>>>    1 file changed, 16 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/net/wireless/iwlwifi/mvm/tx.c b/drivers/net/wireless/iwlwifi/mvm/tx.c
>>> index 5046833..046e50d 100644
>>> --- a/drivers/net/wireless/iwlwifi/mvm/tx.c
>>> +++ b/drivers/net/wireless/iwlwifi/mvm/tx.c
>> [...]
>>> @@ -1034,6 +1035,20 @@ static int iwl_mvm_tx_tso(struct iwl_mvm *mvm, struct sk_buff *skb_gso,
>>>    		}
>>>
>>>    		__skb_queue_tail(mpdus_skb, skb);
>>> +		sum_truesize += skb->truesize;
>>> +	}
>>> +
>>> +	/* Release the backpressure on the socket only when
>>> +	 * the last segment is released.
>>> +	 */
>>> +	if (skb_gso->destructor == sock_wfree) {
>
> I need to change the destructor function here as per Eric's comment.
>
>>> +		struct sk_buff *tail = mpdus_skb->prev;
>>> +
>>> +		swap(tail->truesize, skb_gso->truesize);
>>> +		swap(tail->destructor, skb_gso->destructor);
>>> +		swap(tail->sk, skb_gso->sk);
>>> +                atomic_add(sum_truesize - skb_gso->truesize,
>>
>>      Please indent using tabs, not spaces.
>
> I am happy this is the only flaw you found ;)

    It just jumped into my eyes. :-)

> Sure - I'll fix. And I'll remove the Change-ID and checkpatch will be
> happy.

    DaveM allows that tag in the networking patches, IIRC.

> No worries ;)

>>
>>> +                           &skb_gso->sk->sk_wmem_alloc);
>>>    	}
>>>
>>>    	ret = 0;

MBR, Sergei

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