netdev - Re: [PATCH net-next v4 6/6] Create netdev->neighbour association

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Message-ID: <20241015235441.69622-1-kuniyu@amazon.com>
Date: Tue, 15 Oct 2024 16:54:41 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <gnaaman@...venets.com>
CC: <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<kuniyu@...zon.com>, <netdev@...r.kernel.org>, <pabeni@...hat.com>
Subject: Re: [PATCH net-next v4 6/6] Create netdev->neighbour association

From: Gilad Naaman <gnaaman@...venets.com>
Date: Tue, 15 Oct 2024 16:59:26 +0000
> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> index 61b5f0d4896a..dbfd27f79bb8 100644
> --- a/net/core/neighbour.c
> +++ b/net/core/neighbour.c
> @@ -61,6 +61,19 @@ static int pneigh_ifdown_and_unlock(struct neigh_table *tbl,
>  static const struct seq_operations neigh_stat_seq_ops;
>  #endif
>  
> +static int family_to_neightbl_index(int family)
> +{

Let's return hlist_head * like this:

static hlist_head *neigh_get_dev_table(struct net_device *dev, int family)
{
	int i;

	switch (family) {
	case default:
		DEBUG_NET_WARN_ON_ONCE(1);
		fallthrough; /* to avoid panic by null-ptr-deref */
	case AF_INET:
		i = NEIGH_ARP_TABLE;
		break;
	case AF_INET6:
		i = NEIGH_ND_TABLE;
		break;
	}

	return &dev->neighbours[i];
}


>  @@ -357,46 +371,45 @@ static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev,
>  			    bool skip_perm)
>  {
>  	int i;
> +	struct neighbour *n;
> +	struct hlist_node *tmp;

nit: reverse xmas tree order.

and cache hlist_head * from neigh_get_dev_table().

>  	struct neigh_hash_table *nht;

nht is no longer used ?


>  
> +	i = family_to_neightbl_index(tbl->family);
> +
>  	nht = rcu_dereference_protected(tbl->nht,
>  					lockdep_is_held(&tbl->lock));
>  
> -	for (i = 0; i < (1 << nht->hash_shift); i++) {
> -		struct neighbour *n;
> -
> -		neigh_for_each(n, &nht->hash_heads[i]) {
> -			if (dev && n->dev != dev)
> -				continue;
> -			if (skip_perm && n->nud_state & NUD_PERMANENT)
> -				continue;
> +	hlist_for_each_entry_safe(n, tmp, &dev->neighbours[i], dev_list) {
> +		if (skip_perm && n->nud_state & NUD_PERMANENT)
> +			continue;
>  
> -			hlist_del_rcu(&n->hash);
> -			write_lock(&n->lock);
> -			neigh_del_timer(n);
> -			neigh_mark_dead(n);
> -			if (refcount_read(&n->refcnt) != 1) {
> -				/* The most unpleasant situation.
> -				   We must destroy neighbour entry,
> -				   but someone still uses it.
> -
> -				   The destroy will be delayed until
> -				   the last user releases us, but
> -				   we must kill timers etc. and move
> -				   it to safe state.
> -				 */
> -				__skb_queue_purge(&n->arp_queue);
> -				n->arp_queue_len_bytes = 0;
> -				WRITE_ONCE(n->output, neigh_blackhole);
> -				if (n->nud_state & NUD_VALID)
> -					n->nud_state = NUD_NOARP;
> -				else
> -					n->nud_state = NUD_NONE;
> -				neigh_dbg(2, "neigh %p is stray\n", n);
> -			}
> -			write_unlock(&n->lock);
> -			neigh_cleanup_and_release(n);
> +		hlist_del_rcu(&n->hash);
> +		hlist_del_rcu(&n->dev_list);
> +		write_lock(&n->lock);
> +		neigh_del_timer(n);
> +		neigh_mark_dead(n);
> +		if (refcount_read(&n->refcnt) != 1) {
> +			/* The most unpleasant situation.
> +			 * We must destroy neighbour entry,
> +			 * but someone still uses it.
> +			 *
> +			 * The destroy will be delayed until
> +			 * the last user releases us, but
> +			 * we must kill timers etc. and move
> +			 * it to safe state.
> +			 */
> +			__skb_queue_purge(&n->arp_queue);
> +			n->arp_queue_len_bytes = 0;
> +			WRITE_ONCE(n->output, neigh_blackhole);
> +			if (n->nud_state & NUD_VALID)
> +				n->nud_state = NUD_NOARP;
> +			else
> +				n->nud_state = NUD_NONE;
> +			neigh_dbg(2, "neigh %p is stray\n", n);
>  		}
> +		write_unlock(&n->lock);
> +		neigh_cleanup_and_release(n);
>  	}
>  }
>  
> @@ -672,6 +685,10 @@ ___neigh_create(struct neigh_table *tbl, const void *pkey,
>  	if (want_ref)
>  		neigh_hold(n);
>  	hlist_add_head_rcu(&n->hash, &nht->hash_heads[hash_val]);
> +
> +	error = family_to_neightbl_index(tbl->family);
> +	hlist_add_head_rcu(&n->dev_list, &dev->neighbours[error]);

Let's use neigh_dev_get_table() directly.

> +
>  	write_unlock_bh(&tbl->lock);
>  	neigh_dbg(2, "neigh %p is created\n", n);
>  	rc = n;