Subject: Re: [PATCH] conntrack: use SLAB_DESTROY_BY_RCU for nf_conn structs

From: Patrick McHardy <[email-masked]>
Date: Wed, 25 Mar 2009 19:05:09 +0100

Eric Dumazet wrote:
> Hi Patrick
> 
> Here is the patch I had the time to test this time...
> No problem so far on my machine.
> I did a UDP flood stress.

Thanks Eric. Most parts looks good, just two questions below:

> diff --git a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c
> index 6ba5c55..fcbcf62 100644
> --- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c
> +++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c
> @@ -25,30 +25,30 @@ struct ct_iter_state {
>  	unsigned int bucket;
>  };
>  
> -static struct hlist_node *ct_get_first(struct seq_file *seq)
> +static struct hlist_nulls_node *ct_get_first(struct seq_file *seq)
>  {
>  	struct net *net = seq_file_net(seq);
>  	struct ct_iter_state *st = seq->private;
> -	struct hlist_node *n;
> +	struct hlist_nulls_node *n;
>  
>  	for (st->bucket = 0;
>  	     st->bucket < nf_conntrack_htable_size;
>  	     st->bucket++) {
>  		n = rcu_dereference(net->ct.hash[st->bucket].first);
> -		if (n)
> +		if (!is_a_nulls(n))
>  			return n;
>  	}
>  	return NULL;
>  }

Don't we need to make sure the entry is not reused while dumping
it?

> diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
> index a51bdac..6066144 100644
> --- a/net/netfilter/nf_conntrack_helper.c
> +++ b/net/netfilter/nf_conntrack_helper.c
> @@ -158,6 +158,7 @@ static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
>  	struct nf_conntrack_tuple_hash *h;
>  	struct nf_conntrack_expect *exp;
>  	const struct hlist_node *n, *next;
> +	const struct hlist_nulls_node *nn;
>  	unsigned int i;
>  
>  	/* Get rid of expectations */
> @@ -174,10 +175,10 @@ static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
>  	}
>  
>  	/* Get rid of expecteds, set helpers to NULL. */
> -	hlist_for_each_entry(h, n, &net->ct.unconfirmed, hnode)
> +	hlist_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
>  		unhelp(h, me);
>  	for (i = 0; i < nf_conntrack_htable_size; i++) {
> -		hlist_for_each_entry(h, n, &net->ct.hash[i], hnode)
> +		hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
>  			unhelp(h, me);
>  	}
>  }
> @@ -217,7 +218,7 @@ int nf_conntrack_helper_init(void)
>  
>  	nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
>  	nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
> -						  &nf_ct_helper_vmalloc);
> +						  &nf_ct_helper_vmalloc, 0);

This should be "1" I think since it wants a hlist_nulls hash.