linux-kernel - Re: [PATCH 1/4] mm/hwpoison: fix traverse hugetlbfs page to avoid printk flood

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Date:	Mon, 02 Sep 2013 14:34:13 -0400
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Wanpeng Li <liwanp@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Tony Luck <tony.luck@...el.com>, gong.chen@...ux.intel.com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] mm/hwpoison: fix traverse hugetlbfs page to avoid
 printk flood

On Mon, Sep 02, 2013 at 08:33:41PM +0800, Wanpeng Li wrote:
> madvise_hwpoison won't check if the page is small page or huge page and traverse 
> in small page granularity against the range unconditional, which result in a printk 
> flood "MCE xxx: already hardware poisoned" if the page is huge page. This patch fix 
> it by increase compound_order(compound_head(page)) for huge page iterator.
> 
> Testcase:
> 
> #define _GNU_SOURCE
> #include <stdlib.h>
> #include <stdio.h>
> #include <sys/mman.h>
> #include <unistd.h>
> #include <fcntl.h>
> #include <sys/types.h>
> #include <errno.h>
> 
> #define PAGES_TO_TEST 3
> #define PAGE_SIZE	4096 * 512
> 
> int main(void)
> {
> 	char *mem;
> 	int i;
> 
> 	mem = mmap(NULL, PAGES_TO_TEST * PAGE_SIZE,
> 			PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, 0, 0);
> 
> 	if (madvise(mem, PAGES_TO_TEST * PAGE_SIZE, MADV_HWPOISON) == -1)
> 		return -1;
> 	
> 	munmap(mem, PAGES_TO_TEST * PAGE_SIZE);
> 
> 	return 0;
> }
> 
> Signed-off-by: Wanpeng Li <liwanp@...ux.vnet.ibm.com>

Reviewed-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>

> ---
>  mm/madvise.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 6975bc8..539eeb9 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -343,10 +343,11 @@ static long madvise_remove(struct vm_area_struct *vma,
>   */
>  static int madvise_hwpoison(int bhv, unsigned long start, unsigned long end)
>  {
> +	struct page *p;
>  	if (!capable(CAP_SYS_ADMIN))
>  		return -EPERM;
> -	for (; start < end; start += PAGE_SIZE) {
> -		struct page *p;
> +	for (; start < end; start += PAGE_SIZE <<
> +				compound_order(compound_head(p))) {
>  		int ret;
>  
>  		ret = get_user_pages_fast(start, 1, 0, &p);
> -- 
> 1.8.1.2
>
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