Re: [PATCH nf-next] netfilter: nft_set_rbtree: use seqcount to avoid lock in most cases

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Wed, Jul 26, 2017 at 01:15:06PM +0200, Pablo Neira Ayuso wrote:
> On Wed, Jul 26, 2017 at 02:09:41AM +0200, Florian Westphal wrote:
> [...]
> > @@ -144,7 +159,9 @@ static int nft_rbtree_insert(const struct net *net, const struct nft_set *set,
> >  	int err;
> >  
> >  	write_lock_bh(&priv->lock);
> > +	write_seqcount_begin(&priv->count);
> >  	err = __nft_rbtree_insert(net, set, rbe, ext);
> > +	write_seqcount_end(&priv->count);
> >  	write_unlock_bh(&priv->lock);
> >  
> >  	return err;
> > @@ -158,7 +175,9 @@ static void nft_rbtree_remove(const struct net *net,
> >  	struct nft_rbtree_elem *rbe = elem->priv;
> >  
> >  	write_lock_bh(&priv->lock);
> 
> Do we need the spinlock anymore? This is protected by mutex from
> userspace, and we have no support for neither timeouts nor dynamic set
> population from packet path yet.

Forget this, I overlook we have a slow path in case seq mismatches.