netdev - Re: [RFC PATCH net-next 15/22] nexthop: Emit a notification when a nexthop group is reduced

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Date:   Tue, 8 Sep 2020 09:33:42 -0600
From:   David Ahern <dsahern@...il.com>
To:     Ido Schimmel <idosch@...sch.org>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org, roopa@...dia.com,
        mlxsw@...dia.com, Ido Schimmel <idosch@...dia.com>
Subject: Re: [RFC PATCH net-next 15/22] nexthop: Emit a notification when a
 nexthop group is reduced

On 9/8/20 3:10 AM, Ido Schimmel wrote:
> From: Ido Schimmel <idosch@...dia.com>
> 
> When a single nexthop is deleted, the configuration of all the groups
> using the nexthop is effectively modified. In this case, emit a
> notification in the nexthop notification chain for each modified group
> so that listeners would not need to keep track of which nexthops are
> member in which groups.
> 
> In the rare cases where the notification fails, emit an error to the
> kernel log.
> 
> Signed-off-by: Ido Schimmel <idosch@...dia.com>
> ---
>  net/ipv4/nexthop.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
> index 0edc3e73d416..33f611bbce1f 100644
> --- a/net/ipv4/nexthop.c
> +++ b/net/ipv4/nexthop.c
> @@ -893,7 +893,7 @@ static void remove_nh_grp_entry(struct net *net, struct nh_grp_entry *nhge,
>  	struct nexthop *nhp = nhge->nh_parent;
>  	struct nexthop *nh = nhge->nh;
>  	struct nh_group *nhg, *newg;
> -	int i, j;
> +	int i, j, err;
>  
>  	WARN_ON(!nh);
>  
> @@ -941,6 +941,10 @@ static void remove_nh_grp_entry(struct net *net, struct nh_grp_entry *nhge,
>  	list_del(&nhge->nh_list);
>  	nexthop_put(nhge->nh);
>  
> +	err = call_nexthop_notifiers(net, NEXTHOP_EVENT_REPLACE, nhp, NULL);
> +	if (err)
> +		pr_err("Failed to replace nexthop group after nexthop deletion\n");

This should refer to the notifier failing since wrt nexthop code the
structs are ok. extack on the stack and logging that message would be
useful too (or have the users of the notifier log why it fails).

> +
>  	if (nlinfo)
>  		nexthop_notify(RTM_NEWNEXTHOP, nhp, nlinfo);
>  }
>