netdev - RE: [PATCH net] hyperv: Fix the error processing in netvsc

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Date:	Fri, 30 Jan 2015 15:05:00 +0000
From:	Haiyang Zhang <haiyangz@...rosoft.com>
To:	Jason Wang <jasowang@...hat.com>
CC:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	KY Srinivasan <kys@...rosoft.com>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"driverdev-devel@...uxdriverproject.org" 
	<driverdev-devel@...uxdriverproject.org>
Subject: RE: [PATCH net] hyperv: Fix the error processing in netvsc_send()



> -----Original Message-----
> From: Jason Wang [mailto:jasowang@...hat.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.

> 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. It's handled in the same way as errors != -EAGAIN, so we don't
need to check this value specifically.

Thanks,
- Haiyang