netdev - RE: [PATCH net-next] netfilter: nf_conntrack: remove the unneed check for *bucket

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Date:	Mon, 1 Feb 2016 16:39:56 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Florian Westphal' <fw@...len.de>,
	Weidong Wang <wangweidong1@...wei.com>
CC:	"pablo@...filter.org" <pablo@...filter.org>,
	"kaber@...sh.net" <kaber@...sh.net>,
	"kadlec@...ckhole.kfki.hu" <kadlec@...ckhole.kfki.hu>,
	David Miller <davem@...emloft.net>,
	"netfilter-devel@...r.kernel.org" <netfilter-devel@...r.kernel.org>,
	"coreteam@...filter.org" <coreteam@...filter.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net-next] netfilter: nf_conntrack: remove the unneed
 check for *bucket

From: Florian Westphal
> Sent: 30 January 2016 21:30
> Weidong Wang <wangweidong1@...wei.com> wrote:
> > In the 'for(...) {}', the *bucket alwasy < net->ct.htable_size,
> > so remove the check
> > @@ -1383,14 +1383,12 @@ get_next_corpse(struct net *net, int (*iter)(struct nf_conn *i, void *data),
> >  		lockp = &nf_conntrack_locks[*bucket % CONNTRACK_LOCKS];
> >  		local_bh_disable();
> >  		spin_lock(lockp);
> > -		if (*bucket < net->ct.htable_size) {
> 
> AFAIU net->ct.htable_size can shrink between for-test and aquiring
> the bucket lockp, so this additional if-test is needed.

If the table can shrink, can it not also grow - in which case
the references bucket will be incorrect?

	David