netdev - Re: [PATCH net] net: fix __dev_kfree_skb

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Date:   Thu, 23 Feb 2023 09:27:58 +0100
From:   Eric Dumazet <edumazet@...gle.com>
To:     Yunsheng Lin <linyunsheng@...wei.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        eric.dumazet@...il.com
Subject: Re: [PATCH net] net: fix __dev_kfree_skb_any() vs drop monitor

On Thu, Feb 23, 2023 at 1:48 AM Yunsheng Lin <linyunsheng@...wei.com> wrote:
>
> On 2023/2/23 8:07, Eric Dumazet wrote:
> > dev_kfree_skb() is aliased to consume_skb().
> >
> > When a driver is dropping a packet by calling dev_kfree_skb_any()
> > we should propagate the drop reason instead of pretending
> > the packet was consumed.
> >
> > Note: Now we have enum skb_drop_reason we could remove
> > enum skb_free_reason (for linux-6.4)
> >
> > Fixes: e6247027e517 ("net: introduce dev_consume_skb_any()")
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > ---
> >  net/core/dev.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/core/dev.c b/net/core/dev.c
> > index 18dc8d75ead9795163ace74e8e86fe35cb9b7552..2bf60afde1e2e4be4806070754ae7486705c5237 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -3134,8 +3134,10 @@ void __dev_kfree_skb_any(struct sk_buff *skb, enum skb_free_reason reason)
> >  {
> >       if (in_hardirq() || irqs_disabled())
> >               __dev_kfree_skb_irq(skb, reason);
> > +     else if (reason == SKB_REASON_DROPPED)
>
> Perhaps add the unlikely() for the SKB_REASON_DROPPED case
> as it is uesed in data path.

Sure I can do this, I will send a v2.

Note that I plan to switch the whole thing when net-next opens with
something like this
(showing not complete patch of course)

diff --git a/net/core/dev.c b/net/core/dev.c
index 2bf60afde1e2e4be4806070754ae7486705c5237..67baed2c8c5ef6577a2256c02c300947b8a919b7
100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3130,16 +3130,14 @@ void __dev_kfree_skb_irq(struct sk_buff *skb,
enum skb_free_reason reason)
 }
 EXPORT_SYMBOL(__dev_kfree_skb_irq);

-void __dev_kfree_skb_any(struct sk_buff *skb, enum skb_free_reason reason)
+void dev_kfree_skb_any_reason(struct sk_buff *skb, enum skb_drop_reason reason)
 {
        if (in_hardirq() || irqs_disabled())
                __dev_kfree_skb_irq(skb, reason);
-       else if (reason == SKB_REASON_DROPPED)
-               kfree_skb(skb);
        else
-               consume_skb(skb);
+               kfree_skb_reason(skb, reason);
 }
-EXPORT_SYMBOL(__dev_kfree_skb_any);
+EXPORT_SYMBOL(dev_kfree_skb_any_reason);


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