netdev - Re: [PATCH 7/9] netfilter: nft_hash: add support for timeouts

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Message-ID: <20150131121611.GA31500@acer.localdomain>
Date:	Sat, 31 Jan 2015 12:16:12 +0000
From:	Patrick McHardy <kaber@...sh.net>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	tgraf@...g.ch, davem@...emloft.net, David.Laight@...LAB.COM,
	ying.xue@...driver.com, paulmck@...ux.vnet.ibm.com,
	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: Re: [PATCH 7/9] netfilter: nft_hash: add support for timeouts

On 31.01, Herbert Xu wrote:
> On Fri, Jan 30, 2015 at 07:46:32AM +0000, Patrick McHardy wrote:
> >
> > +	mutex_lock(&priv->ht.mutex);
> > +	tbl = rht_dereference(priv->ht.tbl, &priv->ht);
> > +	for (i = 0; i < tbl->size; i++) {
> > +		rht_for_each_entry_safe(he, pos, next, tbl, i, node) {
> > +			if (!nft_set_ext_exists(&he->ext, NFT_SET_EXT_TIMEOUT))
> > +				continue;
> > +			timeout = *nft_set_ext_timeout(&he->ext);
> > +			if (time_before(jiffies, timeout))
> > +				continue;
> > +
> > +			rhashtable_remove(&priv->ht, &he->node);
> > +			nft_hash_elem_destroy(set, he);
> > +		}
> > +	}
> > +	mutex_unlock(&priv->ht.mutex);
> 
> What if somebody is currently walking over the table? Shouldn't
> you do an RCU free here instead of immediately destroying the
> element?

Yes, that's what I meant in mail 0/x regarding the existing races.
Probably will add some fixed sized batching here.
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