On 09/10/2014 01:33 PM, Johannes Berg wrote:
> On Wed, 2014-09-10 at 16:06 -0400, Alexander Duyck wrote:
>> The code for cloning the skb for an acknowledgement was checking to see if
>> the cloned skb was shared and if it was it was then freeing the original
>> skb. Since a clone should never really be shared I suspect that the
>> intention was to avoid freeing the clone if the original was shared. As
>> such I am updating the code so that if the original is shared we free the
>> original and use the clone. This avoids unnecessary work in the next
>> section where we would be cloning the skb if the original is shared.
>
> Thanks, yeah, I admit that this is clearly fishy.
>
>> @@ -2087,7 +2087,7 @@ netdev_tx_t ieee80211_subif_start_xmit(struct sk_buff *skb,
>> if (id >= 0) {
>> info_id = id;
>> info_flags |= IEEE80211_TX_CTL_REQ_TX_STATUS;
>
> Luckily, we practically always go into this path.
>
>> - } else if (skb_shared(skb)) {
>> + } else if (skb_shared(orig_skb)) {
>> kfree_skb(orig_skb);
>> } else {
>> kfree_skb(skb);
>
> We have a clone already so we could just remove the whole "else if" I
> think, but I'm guessing my intent was to keep it accounted to the socket
> where possible rather than freeing the original in all cases.
>
> So yeah, I think this makes sense. Maybe we should add a comment to the
> if though to explain this?
>
> johannes
Actually I think we may need to take a different approach. The reason I
was in this code was to take a look at a possible refcount issue.
I'll be submitting another patch in a few minutes and will probably be
dropping some of this code anyway.
Thanks,
Alex
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