From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A131FC001B2 for ; Fri, 16 Dec 2022 10:10:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230316AbiLPKKt (ORCPT ); Fri, 16 Dec 2022 05:10:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49316 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229625AbiLPKKr (ORCPT ); Fri, 16 Dec 2022 05:10:47 -0500 Received: from mail.netfilter.org (mail.netfilter.org [217.70.188.207]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 9086B6175; Fri, 16 Dec 2022 02:10:45 -0800 (PST) Date: Fri, 16 Dec 2022 11:10:41 +0100 From: Pablo Neira Ayuso To: Julian Anastasov Cc: Arnd Bergmann , Simon Horman , Arnd Bergmann , Jakub Kicinski , Paolo Abeni , Jiri Wiesner , netdev@vger.kernel.org, lvs-devel@vger.kernel.org, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, linux-kernel Subject: Re: [PATCH] ipvs: use div_s64 for signed division Message-ID: References: <20221215170324.2579685-1-arnd@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Hi Julian, On Thu, Dec 15, 2022 at 09:01:59PM +0200, Julian Anastasov wrote: > > Hello, > > On Thu, 15 Dec 2022, Arnd Bergmann wrote: > > > From: Arnd Bergmann > > > > do_div() is only well-behaved for positive numbers, and now warns > > when the first argument is a an s64: > > > > net/netfilter/ipvs/ip_vs_est.c: In function 'ip_vs_est_calc_limits': > > include/asm-generic/div64.h:222:35: error: comparison of distinct pointer types lacks a cast [-Werror] > > 222 | (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \ > > | ^~ > > net/netfilter/ipvs/ip_vs_est.c:694:17: note: in expansion of macro 'do_div' > > 694 | do_div(val, loops); > > net-next already contains fix for this warning > and changes val to u64. Arnd's patch applies fine on top of net-next, maybe he is addressing something else? > > Convert to using the more appropriate div_s64(), which also > > simplifies the code a bit. > > > > Fixes: 705dd3444081 ("ipvs: use kthreads for stats estimation") > > Signed-off-by: Arnd Bergmann > > --- > > net/netfilter/ipvs/ip_vs_est.c | 6 ++---- > > 1 file changed, 2 insertions(+), 4 deletions(-) > > > > diff --git a/net/netfilter/ipvs/ip_vs_est.c b/net/netfilter/ipvs/ip_vs_est.c > > index ce2a1549b304..dbc32f8cf1f9 100644 > > --- a/net/netfilter/ipvs/ip_vs_est.c > > +++ b/net/netfilter/ipvs/ip_vs_est.c > > @@ -691,15 +691,13 @@ static int ip_vs_est_calc_limits(struct netns_ipvs *ipvs, int *chain_max) > > } > > if (diff >= NSEC_PER_SEC) > > continue; > > - val = diff; > > - do_div(val, loops); > > + val = div_s64(diff, loops); > > On CONFIG_X86_32 both versions execute single divl > for our case but div_s64 is not inlined. I'm not expert in > this area but if you think div_u64 is more appropriate then > post another patch. Note that now val is u64 and > min_est is still s32 (can be u32). > > > if (!min_est || val < min_est) { > > min_est = val; > > /* goal: 95usec per chain */ > > val = 95 * NSEC_PER_USEC; > > if (val >= min_est) { > > - do_div(val, min_est); > > - max = (int)val; > > + max = div_s64(val, min_est); > > } else { > > max = 1; > > } > > -- > > 2.35.1 > > Regards > > -- > Julian Anastasov >