Subject: Re: [PATCH net] net: sched: shrink struct qdisc_skb_cb to 28 bytes

From: Stephen Hemminger <[email-masked]>
Date: Thu, 18 Sep 2014 09:26:28 -0700

On Thu, 18 Sep 2014 08:02:05 -0700
Eric Dumazet <[email-masked]> wrote:

> From: Eric Dumazet <[email-masked]>
> 
> We cannot make struct qdisc_skb_cb bigger without impacting IPoIB,
> or increasing skb->cb[] size.
> 
> Commit e0f31d849867 ("flow_keys: Record IP layer protocol in
> skb_flow_dissect()") broke IPoIB.
> 
> Only current offender is sch_choke, and this one do not need an
> absolutely precise flow key.
> 
> If we store 17 bytes of flow key, its more than enough. (Its the actual
> size of flow_keys if it was a packed structure, but we might add new
> fields at the end of it later)
> 
> Signed-off-by: Eric Dumazet <[email-masked]>

Can we add BUILD_BUG to stop next time something smacks this.