linux-kernel - Re: [PATCH net-next] Fix clamp() of ip_vs_conn

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Message-ID: <a0ebe11c-4ca2-d2f3-8e53-0d9f44bfdda0@ssi.bg>
Date: Thu, 19 Dec 2024 07:06:16 +0200 (EET)
From: Julian Anastasov <ja@....bg>
To: David Laight <David.Laight@...LAB.COM>
cc: "'netdev@...r.kernel.org'" <netdev@...r.kernel.org>,
        "'Naresh Kamboju'" <naresh.kamboju@...aro.org>,
        "'Dan Carpenter'" <dan.carpenter@...aro.org>,
        "'pablo@...filter.org'" <pablo@...filter.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "'open list'" <linux-kernel@...r.kernel.org>,
        "'lkft-triage@...ts.linaro.org'" <lkft-triage@...ts.linaro.org>,
        "'Linux Regressions'" <regressions@...ts.linux.dev>,
        "'Linux ARM'" <linux-arm-kernel@...ts.infradead.org>,
        "'netfilter-devel@...r.kernel.org'" <netfilter-devel@...r.kernel.org>,
        Simon Horman <horms@...ge.net.au>, lvs-devel@...r.kernel.org
Subject: Re: [PATCH net-next] Fix clamp() of ip_vs_conn_tab on small memory
 systems.


	Hello,

On Tue, 17 Dec 2024, Julian Anastasov wrote:

> On Sat, 14 Dec 2024, David Laight wrote:
> 
> > The 'max_avail' value is calculated from the system memory
> > size using order_base_2().
> > order_base_2(x) is defined as '(x) ? fn(x) : 0'.
> > The compiler generates two copies of the code that follows
> > and then expands clamp(max, min, PAGE_SHIFT - 12) (11 on 32bit).
> > This triggers a compile-time assert since min is 5.
> 
> 	8 ?
> 
> > 
> > In reality a system would have to have less than 512MB memory

	Also, note that this is 512KB (practically impossible),
not 512MB. So, it can fail only on build.

Regards

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