netdev - Re: [PATCH net] netfilter: nf_tables: prefer kfree

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Message-ID: <YhXusp0zhI8Mob2A@salvia>
Date:   Wed, 23 Feb 2022 09:22:10 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     Florian Westphal <fw@...len.de>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        netfilter-devel@...r.kernel.org, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] netfilter: nf_tables: prefer kfree_rcu(ptr, rcu)
 variant

On Tue, Feb 22, 2022 at 12:07:05PM -0800, Eric Dumazet wrote:
> On Tue, Feb 22, 2022 at 11:46 AM Florian Westphal <fw@...len.de> wrote:
> >
> > Eric Dumazet <eric.dumazet@...il.com> wrote:
> > > From: Eric Dumazet <edumazet@...gle.com>
> > >
> > > While kfree_rcu(ptr) _is_ supported, it has some limitations.
> > >
> > > Given that 99.99% of kfree_rcu() users [1] use the legacy
> > > two parameters variant, and @catchall objects do have an rcu head,
> > > simply use it.
> > >
> > > Choice of kfree_rcu(ptr) variant was probably not intentional.
> >
> > In case someone wondered, this causes expensive
> > sycnhronize_rcu + kfree for each removal operation.
> 
> This fallback to synchronize_rcu() only happens if kvfree_call_rcu() has been
> unable to allocate a new block of memory.
> 
> But yes, I guess I would add a Fixes: tag, because we can easily avoid
> this potential issue.
> 
> Pablo, if not too late:
> 
> Fixes: aaa31047a6d2 ("netfilter: nftables: add catch-all set element support")

Applied, thanks!