[3.19.y-ckt stable] Patch "sch_htb: update backlog as well" has been added to the 3.19.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    sch_htb: update backlog as well

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    https://git.launchpad.net/~canonical-kernel/linux/+git/linux-stable-ckt/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt22.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From f8ae270ea93c420f8970a0788c7ae4e96a3dd56c Mon Sep 17 00:00:00 2001
From: WANG Cong <xiyou.wangcong at gmail.com>
Date: Thu, 25 Feb 2016 14:55:02 -0800
Subject: sch_htb: update backlog as well

[ Upstream commit 431e3a8e36a05a37126f34b41aa3a5a6456af04e ]

We saw qlen!=0 but backlog==0 on our production machine:

qdisc htb 1: dev eth0 root refcnt 2 r2q 10 default 1 direct_packets_stat 0 ver 3.17
 Sent 172680457356 bytes 222469449 pkt (dropped 0, overlimits 123575834 requeues 0)
 backlog 0b 72p requeues 0

The problem is we only count qlen for HTB qdisc but not backlog.
We need to update backlog too when we update qlen, so that we
can at least know the average packet length.

Cc: Jamal Hadi Salim <jhs at mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs at mojatatu.com>
Signed-off-by: Cong Wang <xiyou.wangcong at gmail.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/sched/sch_htb.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 6b118b1..ccff006 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -600,6 +600,7 @@ static int htb_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 		htb_activate(q, cl);
 	}

+	qdisc_qstats_backlog_inc(sch, skb);
 	sch->q.qlen++;
 	return NET_XMIT_SUCCESS;
 }
@@ -889,6 +890,7 @@ static struct sk_buff *htb_dequeue(struct Qdisc *sch)
 ok:
 		qdisc_bstats_update(sch, skb);
 		qdisc_unthrottled(sch);
+		qdisc_qstats_backlog_dec(sch, skb);
 		sch->q.qlen--;
 		return skb;
 	}
@@ -955,6 +957,7 @@ static unsigned int htb_drop(struct Qdisc *sch)
 			unsigned int len;
 			if (cl->un.leaf.q->ops->drop &&
 			    (len = cl->un.leaf.q->ops->drop(cl->un.leaf.q))) {
+				sch->qstats.backlog -= len;
 				sch->q.qlen--;
 				if (!cl->un.leaf.q->q.qlen)
 					htb_deactivate(q, cl);
@@ -984,12 +987,12 @@ static void htb_reset(struct Qdisc *sch)
 			}
 			cl->prio_activity = 0;
 			cl->cmode = HTB_CAN_SEND;
-
 		}
 	}
 	qdisc_watchdog_cancel(&q->watchdog);
 	__skb_queue_purge(&q->direct_queue);
 	sch->q.qlen = 0;
+	sch->qstats.backlog = 0;
 	memset(q->hlevel, 0, sizeof(q->hlevel));
 	memset(q->row_mask, 0, sizeof(q->row_mask));
 	for (i = 0; i < TC_HTB_NUMPRIO; i++)
--
2.7.4