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Date: Thu, 30 Aug 2018 11:07:26 +0200
From: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: linux-wireless <linux-wireless@vger.kernel.org>
Subject: Re: [PATCH v2] mac80211: do not aggregate frames if max_frags is set
 to one
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On Aug 30, Johannes Berg wrote:
> On Thu, 2018-08-30 at 11:00 +0200, Lorenzo Bianconi wrote:
> > > On Thu, 2018-08-30 at 10:50 +0200, Lorenzo Bianconi wrote:
> > > > 
> > > > ack, I agree. Do you want I send a patch to fix it?
> > > 
> > > I have it written now, I'll just commit & send it out.
> > 
> > Sound good, thx :)
> > 
> > > 
> > > > > Hmm, not sure I follow? "head" is the A-MSDU, containing the A-MSDU
> > > > > header and the first subframe in skb->data (and/or frags), with the
> > > > > subframes 2..N in the fraglist.
> > > > > 
> > > > > So I think this is right?
> > > > 
> > > > yep, correct. But when we are analyzing the second subframe what is the correct value for 'n'?
> > > > 1 or 2? At the moment I guess it is set to 1 if frag_tail is NULL for head.
> > > 
> > > Ah. I guess you're right. So basically setting max_subframes to 1
> > > doesn't avoid A-MSDUs completely, since n will still be 1 when we get
> > > here ... good point, care to send a patch?
> > > 
> > 
> > ack, I will send a patch for it
> 
> The same is true for nfrags, btw, no?

I do not think so since for nfrags we have:
nfrags = 1 + skb_shinfo(skb)->nr_frags;
nfrags += 1 + skb_shinfo(head)->nr_frags;

and even if frag_tail is NULL we will have nfrags = 2.

Agree?

Lorenzo

> 
> johannes