On Fri, Mar 4, 2022 at 1:59 AM Eric Dumazet <edumazet@xxxxxxxxxx> wrote:
>
> On Thu, Mar 3, 2022 at 9:48 AM <menglong8.dong@xxxxxxxxx> wrote:
> >
> > From: Menglong Dong <imagedong@xxxxxxxxxxx>
> >
> > Replace kfree_skb() used in enqueue_to_backlog() with
> > kfree_skb_reason(). The skb rop reason SKB_DROP_REASON_CPU_BACKLOG is
> > introduced for the case of failing to enqueue the skb to the per CPU
> > backlog queue. The further reason can be backlog queue full or RPS
> > flow limition, and I think we meedn't to make further distinctions.
> >
> > Signed-off-by: Menglong Dong <imagedong@xxxxxxxxxxx>
> > ---
> > include/linux/skbuff.h | 6 ++++++
> > include/trace/events/skb.h | 1 +
> > net/core/dev.c | 6 +++++-
> > 3 files changed, 12 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > index 62f9d15ec6ec..d2cf87ff84c2 100644
> > --- a/include/linux/skbuff.h
> > +++ b/include/linux/skbuff.h
> > @@ -402,6 +402,12 @@ enum skb_drop_reason {
> > * outputting (failed to enqueue to
> > * current qdisc)
> > */
> > + SKB_DROP_REASON_CPU_BACKLOG, /* failed to enqueue the skb to
> > + * the per CPU backlog queue. This
> > + * can be caused by backlog queue
> > + * full (see netdev_max_backlog in
> > + * net.rst) or RPS flow limit
> > + */
> > SKB_DROP_REASON_MAX,
> > };
> >
> > diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
> > index 80fe15d175e3..29c360b5e114 100644
> > --- a/include/trace/events/skb.h
> > +++ b/include/trace/events/skb.h
> > @@ -47,6 +47,7 @@
> > EM(SKB_DROP_REASON_NEIGH_DEAD, NEIGH_DEAD) \
> > EM(SKB_DROP_REASON_QDISC_EGRESS, QDISC_EGRESS) \
> > EM(SKB_DROP_REASON_QDISC_DROP, QDISC_DROP) \
> > + EM(SKB_DROP_REASON_CPU_BACKLOG, CPU_BACKLOG) \
> > EMe(SKB_DROP_REASON_MAX, MAX)
> >
> > #undef EM
> > diff --git a/net/core/dev.c b/net/core/dev.c
> > index 3280ba2502cd..373fa7a33ffa 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -4541,10 +4541,12 @@ static bool skb_flow_limit(struct sk_buff *skb, unsigned int qlen)
> > static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
> > unsigned int *qtail)
> > {
> > + enum skb_drop_reason reason;
> > struct softnet_data *sd;
> > unsigned long flags;
> > unsigned int qlen;
> >
> > + reason = SKB_DROP_REASON_NOT_SPECIFIED;
> > sd = &per_cpu(softnet_data, cpu);
> >
> > rps_lock_irqsave(sd, &flags);
> > @@ -4566,6 +4568,8 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
> > if (!__test_and_set_bit(NAPI_STATE_SCHED, &sd->backlog.state))
> > napi_schedule_rps(sd);
> > goto enqueue;
> > + } else {
>
> No need for an else {} after a goto xxx;
>
Yeah, this 'else' can be omitted :) Thanks!
>
> > + reason = SKB_DROP_REASON_CPU_BACKLOG;
> > }
> >
> > drop:
> > @@ -4573,7 +4577,7 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
> > rps_unlock_irq_restore(sd, &flags);
> >
> > atomic_long_inc(&skb->dev->rx_dropped);
> > - kfree_skb(skb);
> > + kfree_skb_reason(skb, reason);
> > return NET_RX_DROP;
> > }
> >
> > --
> > 2.35.1
> >
