RE: [PATCH net] hyperv: Fix the error processing in netvsc_send()

[Jason Wang <jasowang@redhat.com>]

On Fri, Jan 30, 2015 at 11:05 PM, Haiyang Zhang 
<haiyangz@microsoft.com> wrote:
> 
> 
>>  -----Original Message-----
>>  From: Jason Wang [mailto:jasowang@redhat.com]
>>  Sent: Friday, January 30, 2015 5:25 AM
>>  > +	if (ret != 0) {
>>  > +		if (section_index != NETVSC_INVALID_INDEX)
>>  > +			netvsc_free_send_slot(net_device, section_index);
>>  
>>  What if ret is -EINVAL or -ENOSPC? Looks like we need free the skb 
>> in
>>  this case also.
> 
> In these cases, skb is freed in netvsc_start_xmit().
> 
> 
>>  >
>>  > +	} else if (skb) {
>>  > +		dev_kfree_skb_any(skb);
>>  
>>  The caller - netvsc_start_xmit() do this also, may be handle this in
>>  caller is better since netvsc_start_xmit() is the only user that 
>> tries
>>  to send a skb?
> 
> When the packet is sent out normally, we frees it in netvsc_send() if 
> it's
> copied to send-buffer. The free is done in netvsc_send(), because the 
> copy
> is also in this function. If it's not copied, it will be freed in 
> another
> function -- netvsc_xmit_completion().
> 
> netvsc_start_xmit() only does free skb in error case.

Ok.
> 
> 
>>  btw, I find during netvsc_start_xmit(), ret was change to -ENOSPC 
>> when
>>  queue_sends[q_idx] < 1. But non of the caller check -ENOSPC in fact?
> 
> In this case, we don't request re-send, so set ret to a value other 
> than
> -EAGAIN. 

Why not? We have available slots for it to be sent now. Dropping the 
packet in this case may cause out of order sending.
> It's handled in the same way as errors != -EAGAIN, so we don't
> need to check this value specifically.

Thanks