linux-kernel - Re: [PATCH 1/3] HWPOISON: fix action

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Message-ID: <20120823093330.GC12745@localhost>
Date:	Thu, 23 Aug 2012 17:33:30 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	Andi Kleen <andi.kleen@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tony Luck <tony.luck@...el.com>,
	Rik van Riel <riel@...hat.com>,
	Jun'ichi Nomura <j-nomura@...jp.nec.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] HWPOISON: fix action_result() to print out
 dirty/clean

On Wed, Aug 22, 2012 at 11:17:33AM -0400, Naoya Horiguchi wrote:
> action_result() fails to print out "dirty" even if an error occurred on a
> dirty pagecache, because when we check PageDirty in action_result() it was
> cleared after page isolation even if it's dirty before error handling. This
> can break some applications that monitor this message, so should be fixed.
> 
> There are several callers of action_result() except page_action(), but
> either of them are not for LRU pages but for free pages or kernel pages,
> so we don't have to consider dirty or not for them.
> 
> Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Reviewed-by: Andi Kleen <ak@...ux.intel.com>
> ---
>  mm/memory-failure.c | 22 +++++++++-------------
>  1 file changed, 9 insertions(+), 13 deletions(-)
> 
> diff --git v3.6-rc1.orig/mm/memory-failure.c v3.6-rc1/mm/memory-failure.c
> index a6e2141..79dfb2f 100644
> --- v3.6-rc1.orig/mm/memory-failure.c
> +++ v3.6-rc1/mm/memory-failure.c
> @@ -779,16 +779,16 @@ static struct page_state {
>  	{ compound,	compound,	"huge",		me_huge_page },
>  #endif
>  
> -	{ sc|dirty,	sc|dirty,	"swapcache",	me_swapcache_dirty },
> -	{ sc|dirty,	sc,		"swapcache",	me_swapcache_clean },
> +	{ sc|dirty,	sc|dirty,	"dirty swapcache",	me_swapcache_dirty },
> +	{ sc|dirty,	sc,		"clean swapcache",	me_swapcache_clean },
>  
> -	{ unevict|dirty, unevict|dirty,	"unevictable LRU", me_pagecache_dirty},
> -	{ unevict,	unevict,	"unevictable LRU", me_pagecache_clean},
> +	{ unevict|dirty, unevict|dirty,	"dirty unevictable LRU", me_pagecache_dirty },
> +	{ unevict,	unevict,	"clean unevictable LRU", me_pagecache_clean },
>  
> -	{ mlock|dirty,	mlock|dirty,	"mlocked LRU",	me_pagecache_dirty },
> -	{ mlock,	mlock,		"mlocked LRU",	me_pagecache_clean },
> +	{ mlock|dirty,	mlock|dirty,	"dirty mlocked LRU",	me_pagecache_dirty },
> +	{ mlock,	mlock,		"clean mlocked LRU",	me_pagecache_clean },
>  
> -	{ lru|dirty,	lru|dirty,	"LRU",		me_pagecache_dirty },
> +	{ lru|dirty,	lru|dirty,	"dirty LRU",	me_pagecache_dirty },
>  	{ lru|dirty,	lru,		"clean LRU",	me_pagecache_clean },

According to the set_page_dirty() comment, the dirty bit might be set
outside the page lock (however I don't know any concrete examples).
That means the word "clean" is not 100% right.  That's probably why we
only report "dirty LRU" and didn't say "clean LRU".

Thanks,
Fengguang

>  	/*
> @@ -812,12 +812,8 @@ static struct page_state {
>  
>  static void action_result(unsigned long pfn, char *msg, int result)
>  {
> -	struct page *page = pfn_to_page(pfn);
> -
> -	printk(KERN_ERR "MCE %#lx: %s%s page recovery: %s\n",
> -		pfn,
> -		PageDirty(page) ? "dirty " : "",
> -		msg, action_name[result]);
> +	pr_err("MCE %#lx: %s page recovery: %s\n",
> +		pfn, msg, action_name[result]);
>  }
>  
>  static int page_action(struct page_state *ps, struct page *p,
> -- 
> 1.7.11.4
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