linux-kernel - Re: [RFC][PATCH] HWPOISON: remove the unsafe __set_page

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Message-ID: <20090926034936.GK30185@one.firstfloor.org>
Date:	Sat, 26 Sep 2009 05:49:36 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Nick Piggin <npiggin@...e.de>,
	Andi Kleen <andi@...stfloor.org>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH] HWPOISON: remove the unsafe __set_page_locked()

On Sat, Sep 26, 2009 at 11:15:37AM +0800, Wu Fengguang wrote:
> The swap cache and page cache code assume that they 'own' the newly
> allocated page and therefore can disregard the locking rules. However
> now hwpoison can hit any time on any page.
> 
> So use the safer lock_page()/trylock_page(). The main intention is not
> to close such a small time window of memory corruption. But to avoid
> kernel oops that may result from such races, and also avoid raising
> false alerts in hwpoison stress tests.
> 
> This in theory will slightly increase page cache/swap cache overheads,
> however it seems to be too small to be measurable in benchmark.

Thanks. Can you please describe what benchmarks you used?

Acked-by: Andi Kleen <ak@...ux.intel.com>
-andi
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