net: sched: restrict use of qstats qlen

This removes the use of qstats->qlen variable from the classifiers
and makes it an explicit argument to gnet_stats_copy_queue().

The qlen represents the qdisc queue length and is packed into
the qstats at the last moment before passnig to user space. By
handling it explicitely we avoid, in the percpu stats case, having
to figure out which per_cpu variable to put it in.

It would probably be best to remove it from qstats completely
but qstats is a user space ABI and can't be broken. A future
patch could make an internal only qstats structure that would
avoid having to allocate an additional u32 variable on the
Qdisc struct. This would make the qstats struct 128bits instead
of 128+32.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 2862bc61a358..ca00ea8e84dc 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1318,6 +1318,7 @@ static int tc_fill_qdisc(struct sk_buff *skb, struct Qdisc *q, u32 clid,
         unsigned char *b = skb_tail_pointer(skb);
         struct gnet_dump d;
         struct qdisc_size_table *stab;
+        __u32 qlen;
 
         cond_resched();
         nlh = nlmsg_put(skb, portid, seq, event, sizeof(*tcm), flags);
@@ -1335,7 +1336,7 @@ static int tc_fill_qdisc(struct sk_buff *skb, struct Qdisc *q, u32 clid,
                 goto nla_put_failure;
         if (q->ops->dump && q->ops->dump(q, skb) < 0)
                 goto nla_put_failure;
-        q->qstats.qlen = q->q.qlen;
+        qlen = q->q.qlen;
 
         stab = rtnl_dereference(q->stab);
         if (stab && qdisc_dump_stab(skb, stab) < 0)
@@ -1353,7 +1354,7 @@ static int tc_fill_qdisc(struct sk_buff *skb, struct Qdisc *q, u32 clid,
 
         if (gnet_stats_copy_basic(&d, cpu_bstats, &q->bstats) < 0 ||
             gnet_stats_copy_rate_est(&d, &q->bstats, &q->rate_est) < 0 ||
-            gnet_stats_copy_queue(&d, &q->qstats) < 0)
+            gnet_stats_copy_queue(&d, &q->qstats, qlen) < 0)
                 goto nla_put_failure;
 
         if (gnet_stats_finish_copy(&d) < 0)