linux-kernel - Re: [PATCH]vmscan: handle underflow for get_scan

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Message-ID: <20100406053644.GA14183@sli10-desk.sh.intel.com>
Date:	Tue, 6 Apr 2010 13:36:44 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	"Wu, Fengguang" <fengguang.wu@...el.com>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH]vmscan: handle underflow for get_scan_ratio

On Tue, Apr 06, 2010 at 01:03:25PM +0800, Wu, Fengguang wrote:
> Shaohua,
> 
> > +		scan = zone_nr_lru_pages(zone, sc, l);
> > +		if (priority) {
> > +			scan >>= priority;
> > +			scan = (scan * fraction[file] / denominator[file]);
> 
> Ah, the (scan * fraction[file]) may overflow in 32bit kernel!
good catch. will change it to u64.
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