linux-kernel - Re: [PATCH] [10/16] HWPOISON: Handle poisoned pages in set_page

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Message-ID: <20090609095920.GD14820@wotan.suse.de>
Date:	Tue, 9 Jun 2009 11:59:20 +0200
From:	Nick Piggin <npiggin@...e.de>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, fengguang.wu@...el.com
Subject: Re: [PATCH] [10/16] HWPOISON: Handle poisoned pages in set_page_dirty()

On Wed, Jun 03, 2009 at 08:46:43PM +0200, Andi Kleen wrote:
> 
> Bail out early in set_page_dirty for poisoned pages. We don't want any
> of the dirty accounting done or file system write back started, because
> the page will be just thrown away.

I don't agree with adding overhead to fastpaths like this. Your
MCE handler should have already taken care of this so I can't
see what it can gain.

> 
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> 
> ---
>  mm/page-writeback.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> Index: linux/mm/page-writeback.c
> ===================================================================
> --- linux.orig/mm/page-writeback.c	2009-06-03 19:36:20.000000000 +0200
> +++ linux/mm/page-writeback.c	2009-06-03 19:36:23.000000000 +0200
> @@ -1304,6 +1304,10 @@
>  {
>  	struct address_space *mapping = page_mapping(page);
>  
> +	if (unlikely(PageHWPoison(page))) {
> +		SetPageDirty(page);
> +		return 0;
> +	}
>  	if (likely(mapping)) {
>  		int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
>  #ifdef CONFIG_BLOCK
--
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