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

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Date:	Tue, 6 Apr 2010 13:03:25 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	"Li, Shaohua" <shaohua.li@...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

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!

Thanks,
Fengguang
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