netdev - Re: [PATCH 3/4] sch_api: Allow reducing queue backlog by a negative value

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Date:   Mon, 7 Jan 2019 12:54:22 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Toke Høiland-Jørgensen <toke@...e.dk>,
        netdev@...r.kernel.org
Cc:     cake@...ts.bufferbloat.net,
        Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [PATCH 3/4] sch_api: Allow reducing queue backlog by a negative
 value



On 01/07/2019 11:47 AM, Toke Høiland-Jørgensen wrote:
> From: Toke Høiland-Jørgensen <toke@...hat.com>
> 
> With GSO splitting in sch_cake, we can decrease as well as increase the
> qlen. To make it possible to signal this up the qdisc tree, change
> qdisc_tree_reduce_backlog() to accept signed integer values as the number
> of packets and bytes to reduce the backlog by.


Not sure why this patch is needed, given we use u32 integers
for q.qlen & qstats.backlog

0xFFFFFFFF for n is really -1 once folded...

sch->q.qlen -= n;
sch->qstats.backlog -= len;