linux-kernel - Re: [PATCH net-next v2 1/2] ipvs: add READ_ONCE barrier for ipvs->sysctl

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Message-ID: <CAEivzxd_Lz3o8Qmqq6wyfK_UduVL1Qm9jQ9UJaoE_O7wWPrg-Q@mail.gmail.com>
Date: Thu, 18 Apr 2024 17:01:49 +0200
From: Aleksandr Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
To: Julian Anastasov <ja@....bg>
Cc: horms@...ge.net.au, netdev@...r.kernel.org, lvs-devel@...r.kernel.org, 
	netfilter-devel@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Pablo Neira Ayuso <pablo@...filter.org>, Jozsef Kadlecsik <kadlec@...filter.org>, 
	Florian Westphal <fw@...len.de>
Subject: Re: [PATCH net-next v2 1/2] ipvs: add READ_ONCE barrier for ipvs->sysctl_amemthresh

On Thu, Apr 18, 2024 at 3:23 PM Julian Anastasov <ja@....bg> wrote:
>
>
>         Hello,

Dear Julian,

>
> On Thu, 18 Apr 2024, Alexander Mikhalitsyn wrote:
>
> > Cc: Julian Anastasov <ja@....bg>
> > Cc: Simon Horman <horms@...ge.net.au>
> > Cc: Pablo Neira Ayuso <pablo@...filter.org>
> > Cc: Jozsef Kadlecsik <kadlec@...filter.org>
> > Cc: Florian Westphal <fw@...len.de>
> > Suggested-by: Julian Anastasov <ja@....bg>
> > Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
> > ---
> >  net/netfilter/ipvs/ip_vs_ctl.c | 12 +++++++-----
> >  1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> > index 143a341bbc0a..daa62b8b2dd1 100644
> > --- a/net/netfilter/ipvs/ip_vs_ctl.c
> > +++ b/net/netfilter/ipvs/ip_vs_ctl.c
>
> > @@ -105,7 +106,8 @@ static void update_defense_level(struct netns_ipvs *ipvs)
> >       /* si_swapinfo(&i); */
> >       /* availmem = availmem - (i.totalswap - i.freeswap); */
> >
> > -     nomem = (availmem < ipvs->sysctl_amemthresh);
> > +     amemthresh = max(READ_ONCE(ipvs->sysctl_amemthresh), 0);
> > +     nomem = (availmem < amemthresh);
> >
> >       local_bh_disable();
> >
> > @@ -146,8 +148,8 @@ static void update_defense_level(struct netns_ipvs *ipvs)
> >       case 1:
> >               if (nomem) {
> >                       ipvs->drop_rate = ipvs->drop_counter
> > -                             = ipvs->sysctl_amemthresh /
> > -                             (ipvs->sysctl_amemthresh-availmem);
> > +                             = amemthresh /
> > +                             (amemthresh-availmem);
>
>         Thanks, both patches look ok except that the old styling
> is showing warnings for this patch:
>
> scripts/checkpatch.pl --strict /tmp/file1.patch
>
>         It would be great if you silence them somehow in v3...

Yeah, I have fixed this in v3. Also, I had to split multiple
assignments into different
lines because of:
>CHECK: multiple assignments should be avoided

Now everything looks fine.

>
>         BTW, est_cpulist is masked with current->cpus_mask of the
> sysctl writer process, if that is of any help. That is why I skipped
> it but lets keep it read-only for now...

That's a good point! Probably I'm too conservative ;-)

>
> >                       ipvs->sysctl_drop_packet = 2;
> >               } else {
> >                       ipvs->drop_rate = 0;
> > @@ -156,8 +158,8 @@ static void update_defense_level(struct netns_ipvs *ipvs)
> >       case 2:
> >               if (nomem) {
> >                       ipvs->drop_rate = ipvs->drop_counter
> > -                             = ipvs->sysctl_amemthresh /
> > -                             (ipvs->sysctl_amemthresh-availmem);
> > +                             = amemthresh /
> > +                             (amemthresh-availmem);
> >               } else {
> >                       ipvs->drop_rate = 0;
> >                       ipvs->sysctl_drop_packet = 1;
>
> Regards

Kind regards,
Alex

>
> --
> Julian Anastasov <ja@....bg>
>