linux-kernel - Re: [PATCH] arp: Remove the arp_hh

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Date:   Mon, 22 Feb 2021 09:37:48 +0100
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Yejune Deng <yejune.deng@...il.com>, davem@...emloft.net,
        yoshfuji@...ux-ipv6.org, dsahern@...nel.org, kuba@...nel.org
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel test robot <oliver.sang@...el.com>
Subject: Re: [PATCH] arp: Remove the arp_hh_ops structure



On 2/22/21 4:15 AM, Yejune Deng wrote:
> The arp_hh_ops structure is similar to the arp_generic_ops structure.
> but the latter is more general,so remove the arp_hh_ops structure.
> 
> Fix when took out the neigh->ops assignment:
> 8.973653] #PF: supervisor read access in kernel mode
> [    8.975027] #PF: error_code(0x0000) - not-present page
> [    8.976310] PGD 0 P4D 0
> [    8.977036] Oops: 0000 [#1] SMP PTI
> [    8.977973] CPU: 1 PID: 210 Comm: sd-resolve Not tainted 5.11.0-rc7-02046-g4591591ab715 #1
> [    8.979998] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
> [    8.981996] RIP: 0010:neigh_probe (kbuild/src/consumer/net/core/neighbour.c:1009)
> 

I have a hard time understanding this patch submission.

This seems a mix of a net-next and net material ?



> Reported-by: kernel test robot <oliver.sang@...el.com>

If this is a bug fix, we want a Fixes: tag

This will really help us. Please don't let us guess what is going on.


Also, if this is not a bug fix, this should target net-next tree,
please take a look at Documentation/networking/netdev-FAQ.rst

In short, the stack trace in this changelog seems to be not
related to this patch, maybe a prior version ? We do not want
to keep artifacts of some buggy version that was never merged
into official tree.

Thanks.

> Signed-off-by: Yejune Deng <yejune.deng@...il.com>
> ---
>  net/ipv4/arp.c | 15 ++-------------
>  1 file changed, 2 insertions(+), 13 deletions(-)
> 
> diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
> index 922dd73e5740..9ee59c2e419a 100644
> --- a/net/ipv4/arp.c
> +++ b/net/ipv4/arp.c
> @@ -135,14 +135,6 @@ static const struct neigh_ops arp_generic_ops = {
>  	.connected_output =	neigh_connected_output,
>  };
>  
> -static const struct neigh_ops arp_hh_ops = {
> -	.family =		AF_INET,
> -	.solicit =		arp_solicit,
> -	.error_report =		arp_error_report,
> -	.output =		neigh_resolve_output,
> -	.connected_output =	neigh_resolve_output,
> -};
> -
>  static const struct neigh_ops arp_direct_ops = {
>  	.family =		AF_INET,
>  	.output =		neigh_direct_output,
> @@ -277,12 +269,9 @@ static int arp_constructor(struct neighbour *neigh)
>  			memcpy(neigh->ha, dev->broadcast, dev->addr_len);
>  		}
>  
> -		if (dev->header_ops->cache)
> -			neigh->ops = &arp_hh_ops;
> -		else
> -			neigh->ops = &arp_generic_ops;
> +		neigh->ops = &arp_generic_ops;
>  
> -		if (neigh->nud_state & NUD_VALID)
> +		if (!dev->header_ops->cache && (neigh->nud_state & NUD_VALID))
>  			neigh->output = neigh->ops->connected_output;
>  		else
>  			neigh->output = neigh->ops->output;
>