netdev - Re: [PATCH bpf-next v2 2/8] bpf: XDP metadata RX kfuncs

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Date:   Tue, 22 Nov 2022 22:34:02 -0800
From:   Martin KaFai Lau <martin.lau@...ux.dev>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        song@...nel.org, yhs@...com, john.fastabend@...il.com,
        kpsingh@...nel.org, haoluo@...gle.com, jolsa@...nel.org,
        David Ahern <dsahern@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Anatoly Burakov <anatoly.burakov@...el.com>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Magnus Karlsson <magnus.karlsson@...il.com>,
        Maryam Tahhan <mtahhan@...hat.com>, xdp-hints@...-project.net,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 2/8] bpf: XDP metadata RX kfuncs

On 11/21/22 10:25 AM, Stanislav Fomichev wrote:
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -2576,6 +2576,7 @@ static void bpf_prog_free_deferred(struct work_struct *work)
>   	} else {
>   		bpf_jit_free(aux->prog);
>   	}
> +	dev_put(aux->xdp_netdev);

I think dev_put needs to be done during unregister_netdevice event also. 
Otherwise, a loaded bpf prog may hold the dev for a long time.  May be there is 
ideas in offload.c.

[ ... ]

> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 35972afb6850..ece7f9234b2d 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -2491,7 +2491,8 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr)
>   				 BPF_F_TEST_STATE_FREQ |
>   				 BPF_F_SLEEPABLE |
>   				 BPF_F_TEST_RND_HI32 |
> -				 BPF_F_XDP_HAS_FRAGS))
> +				 BPF_F_XDP_HAS_FRAGS |
> +				 BPF_F_XDP_HAS_METADATA))
>   		return -EINVAL;
>   
>   	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) &&
> @@ -2579,6 +2580,20 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr)
>   	prog->aux->sleepable = attr->prog_flags & BPF_F_SLEEPABLE;
>   	prog->aux->xdp_has_frags = attr->prog_flags & BPF_F_XDP_HAS_FRAGS;
>   
> +	if (attr->prog_flags & BPF_F_XDP_HAS_METADATA) {
> +		/* Reuse prog_ifindex to bind to the device
> +		 * for XDP metadata kfuncs.
> +		 */
> +		prog->aux->offload_requested = false;
> +
> +		prog->aux->xdp_netdev = dev_get_by_index(current->nsproxy->net_ns,
> +							 attr->prog_ifindex);
> +		if (!prog->aux->xdp_netdev) {
> +			err = -EINVAL;
> +			goto free_prog;
> +		}
> +	}