linux-kernel - Re: [PATCH net-next] net: switch to storing KCOV handle directly in sk

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Date:   Wed, 25 Nov 2020 23:42:36 +0100
From:   Marco Elver <elver@...gle.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Johannes Berg <johannes@...solutions.net>,
        Aleksandr Nogikh <a.nogikh@...il.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>, linux-wireless@...r.kernel.org,
        Ido Schimmel <idosch@...sch.org>,
        Florian Westphal <fw@...len.de>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net-next] net: switch to storing KCOV handle directly in sk_buff

On Wed, 25 Nov 2020 at 21:43, Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Wed, 25 Nov 2020 18:34:36 +0100 Marco Elver wrote:
> > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> > index ffe3dcc0ebea..070b1077d976 100644
> > --- a/net/core/skbuff.c
> > +++ b/net/core/skbuff.c
> > @@ -233,6 +233,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
> >       skb->end = skb->tail + size;
> >       skb->mac_header = (typeof(skb->mac_header))~0U;
> >       skb->transport_header = (typeof(skb->transport_header))~0U;
> > +     skb_set_kcov_handle(skb, kcov_common_handle());
> >
> >       /* make sure we initialize shinfo sequentially */
> >       shinfo = skb_shinfo(skb);
> > @@ -249,9 +250,6 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
> >
> >               fclones->skb2.fclone = SKB_FCLONE_CLONE;
> >       }
> > -
> > -     skb_set_kcov_handle(skb, kcov_common_handle());
>
> Why the move?

v2 of the original series had it above. I frankly don't mind.

1. Group it with the other fields above?

2. Leave it at the end here?

> >  out:
> >       return skb;
> >  nodata:
> > @@ -285,8 +283,6 @@ static struct sk_buff *__build_skb_around(struct sk_buff *skb,
> >       memset(shinfo, 0, offsetof(struct skb_shared_info, dataref));
> >       atomic_set(&shinfo->dataref, 1);
> >
> > -     skb_set_kcov_handle(skb, kcov_common_handle());
> > -
> >       return skb;
> >  }
>
> And why are we dropping this?

It wasn't here originally.

> If this was omitted in earlier versions it's just a independent bug,
> I don't think build_skb() will call __alloc_skb(), so we need a to
> set the handle here.

Correct, that was an original omission.

Will send v2.