[PATCH 5.4 153/191] net_sched: sch_fq: properly set sk->sk_pacing_status

Greg Kroah-Hartman
2020-01-02T22:17:04Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit bb3d0b8bf5be61ab1d6f472c43cbf34de17e796b ]

If fq_classify() recycles a struct fq_flow because
a socket structure has been reallocated, we do not
set sk->sk_pacing_status immediately, but later if the
flow becomes detached.

This means that any flow requiring pacing (BBR, or SO_MAX_PACING_RATE)
might fallback to TCP internal pacing, which requires a per-socket
high resolution timer, and therefore more cpu cycles.

Fixes: 218af599fa63 ("tcp: internal implementation for pacing")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sched/sch_fq.c | 17 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)

--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -301,6 +301,9 @@ static struct fq_flow *fq_classify(struc
f->socket_hash != sk->sk_hash)) {
f->credit = q->initial_quantum;
f->socket_hash = sk->sk_hash;
+ if (q->rate_enable)
+ smp_store_release(&sk->sk_pacing_status,
+ SK_PACING_FQ);
if (fq_flow_is_throttled(f))
fq_flow_unset_throttled(q, f);
f->time_next_packet = 0ULL;
@@ -322,8 +325,12 @@ static struct fq_flow *fq_classify(struc

fq_flow_set_detached(f);
f->sk = sk;
- if (skb->sk == sk)
+ if (skb->sk == sk) {
f->socket_hash = sk->sk_hash;
+ if (q->rate_enable)
+ smp_store_release(&sk->sk_pacing_status,
+ SK_PACING_FQ);
+ }
f->credit = q->initial_quantum;

rb_link_node(&f->fq_node, parent, p);
@@ -428,17 +435,9 @@ static int fq_enqueue(struct sk_buff *sk
f->qlen++;
qdisc_qstats_backlog_inc(sch, skb);
if (fq_flow_is_detached(f)) {
- struct sock *sk = skb->sk;
-
fq_flow_add_tail(&q->new_flows, f);
if (time_after(jiffies, f->age + q->flow_refill_delay))
f->credit = max_t(u32, f->credit, q->quantum);
- if (sk && q->rate_enable) {
- if (unlikely(smp_load_acquire(&sk->sk_pacing_status) !=
- SK_PACING_FQ))
- smp_store_release(&sk->sk_pacing_status,
- SK_PACING_FQ);
- }
q->inactive_flows--;
}