Re: [PATCH v2 net-next] net: generalize skb freeing deferral to per-cpu lists

From: Eric Dumazet <edumazet@google.com>
To: Ido Schimmel <idosch@idosch.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
	"David S . Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH v2 net-next] net: generalize skb freeing deferral to per-cpu lists
Date: Wed, 27 Apr 2022 10:59:50 -0700	[thread overview]
Message-ID: <CANn89iK3uzj4MzAyPrjQVR+5fZQaBdopuMEAZGP6QmWeXZj19Q@mail.gmail.com> (raw)
In-Reply-To: <CANn89iLue8fy-6TTEsTwzWAog-KnAcsG19up34621W8Bp+0=NQ@mail.gmail.com>

On Wed, Apr 27, 2022 at 10:11 AM Eric Dumazet <edumazet@google.com> wrote:
>
> On Wed, Apr 27, 2022 at 9:53 AM Eric Dumazet <edumazet@google.com> wrote:
> >
> > On Wed, Apr 27, 2022 at 8:34 AM Ido Schimmel <idosch@idosch.org> wrote:
> > >
> >
> > >
> > > Eric, with this patch I'm seeing memory leaks such as these [1][2] after
> > > boot. The system is using the igb driver for its management interface
> > > [3]. The leaks disappear after reverting the patch.
> > >
> > > Any ideas?
> > >
> >
> > No idea, skbs allocated to send an ACK can not be stored in receive
> > queue, I guess this is a kmemleak false positive.
> >
> > Stress your host for hours, and check if there are real kmemleaks, as
> > in memory being depleted.
>
> AT first when I saw your report I wondered if the following was needed,
> but I do not think so. Nothing in __kfree_skb(skb) cares about skb->next.
>
> But you might give it a try, maybe I am wrong.
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 611bd719706412723561c27753150b27e1dc4e7a..9dc3443649b962586cc059899ac3d71e9c7a3559
> 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -6594,6 +6594,7 @@ static void skb_defer_free_flush(struct softnet_data *sd)
>
>         while (skb != NULL) {
>                 next = skb->next;
> +               skb_mark_not_on_list(skb);
>                 __kfree_skb(skb);
>                 skb = next;
>         }

Oh well, there is definitely a leak, sorry for that.