[PATCH] MCE: fix an error of mce_bad_pages statistics

[PATCH] MCE: fix an error of mce_bad_pages statistics

[Xishi Qiu]

On x86 platform, if we use "/sys/devices/system/memory/soft_offline_page" to offline a
free page twice, the value of mce_bad_pages will be added twice. So this is an error,
since the page was already marked HWPoison, we should skip the page and don't add the
value of mce_bad_pages.

$ cat /proc/meminfo | grep HardwareCorrupted

soft_offline_page()
	get_any_page()
		atomic_long_add(1, &mce_bad_pages)

The free page which marked HWPoison is still managed by page buddy allocator. So when
offlining it again, get_any_page() always returns 0 with
"pr_info("%s: %#lx free buddy page\n", __func__, pfn);".

When page is allocated, the PageBuddy is removed in bad_page(), then get_any_page()
returns -EIO with pr_info("%s: %#lx: unknown zero refcount page type %lx\n", so
mce_bad_pages will not be added.

Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
i>>?Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
---
 mm/memory-failure.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 8b20278..02a522e 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1375,6 +1375,11 @@ static int get_any_page(struct page *p, unsigned long pfn, int flags)
 	if (flags & MF_COUNT_INCREASED)
 		return 1;

+	if (PageHWPoison(p)) {
+		pr_info("%s: %#lx page already poisoned\n", __func__, pfn);
+		return -EBUSY;
+	}
+
 	/*
 	 * The lock_memory_hotplug prevents a race with memory hotplug.
 	 * This is a big hammer, a better would be nicer.
-- 
1.7.6.1


--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] MCE: fix an error of mce_bad_pages statistics

[Borislav Petkov]

On Fri, Dec 07, 2012 at 10:53:41AM +0800, Xishi Qiu wrote:
> On x86 platform, if we use "/sys/devices/system/memory/soft_offline_page" to offline a
> free page twice, the value of mce_bad_pages will be added twice. So this is an error,
> since the page was already marked HWPoison, we should skip the page and don't add the
> value of mce_bad_pages.
> 
> $ cat /proc/meminfo | grep HardwareCorrupted
> 
> soft_offline_page()
> 	get_any_page()
> 		atomic_long_add(1, &mce_bad_pages)
> 
> The free page which marked HWPoison is still managed by page buddy allocator. So when
> offlining it again, get_any_page() always returns 0 with
> "pr_info("%s: %#lx free buddy page\n", __func__, pfn);".
> 
> When page is allocated, the PageBuddy is removed in bad_page(), then get_any_page()
> returns -EIO with pr_info("%s: %#lx: unknown zero refcount page type %lx\n", so
> mce_bad_pages will not be added.
> 
> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
> i>>?Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
> ---
>  mm/memory-failure.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 8b20278..02a522e 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1375,6 +1375,11 @@ static int get_any_page(struct page *p, unsigned long pfn, int flags)
>  	if (flags & MF_COUNT_INCREASED)
>  		return 1;
> 
> +	if (PageHWPoison(p)) {
> +		pr_info("%s: %#lx page already poisoned\n", __func__, pfn);
> +		return -EBUSY;
> +	}

Shouldn't this be done in soft_offline_page() instead, like it is done
in soft_offline_huge_page() for hugepages?

Thanks.

-- 
Regards/Gruss,
    Boris.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] MCE: fix an error of mce_bad_pages statistics

[Xishi Qiu]

On 2012/12/7 15:25, Borislav Petkov wrote:

> On Fri, Dec 07, 2012 at 10:53:41AM +0800, Xishi Qiu wrote:
>> On x86 platform, if we use "/sys/devices/system/memory/soft_offline_page" to offline a
>> free page twice, the value of mce_bad_pages will be added twice. So this is an error,
>> since the page was already marked HWPoison, we should skip the page and don't add the
>> value of mce_bad_pages.
>>
>> $ cat /proc/meminfo | grep HardwareCorrupted
>>
>> soft_offline_page()
>> 	get_any_page()
>> 		atomic_long_add(1, &mce_bad_pages)
>>
>> The free page which marked HWPoison is still managed by page buddy allocator. So when
>> offlining it again, get_any_page() always returns 0 with
>> "pr_info("%s: %#lx free buddy page\n", __func__, pfn);".
>>
>> When page is allocated, the PageBuddy is removed in bad_page(), then get_any_page()
>> returns -EIO with pr_info("%s: %#lx: unknown zero refcount page type %lx\n", so
>> mce_bad_pages will not be added.
>>
>> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
>> i>>?Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
>> ---
>>  mm/memory-failure.c |    5 +++++
>>  1 files changed, 5 insertions(+), 0 deletions(-)
>>
>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>> index 8b20278..02a522e 100644
>> --- a/mm/memory-failure.c
>> +++ b/mm/memory-failure.c
>> @@ -1375,6 +1375,11 @@ static int get_any_page(struct page *p, unsigned long pfn, int flags)
>>  	if (flags & MF_COUNT_INCREASED)
>>  		return 1;
>>
>> +	if (PageHWPoison(p)) {
>> +		pr_info("%s: %#lx page already poisoned\n", __func__, pfn);
>> +		return -EBUSY;
>> +	}
> 
> Shouldn't this be done in soft_offline_page() instead, like it is done
> in soft_offline_huge_page() for hugepages?
> 
> Thanks.
> 

Hi Borislav, you mean we should move this to the beginning of soft_offline_page()?

soft_offline_page()
{
	...
	get_any_page()
	...
	/*
	 * Synchronized using the page lock with memory_failure()
	 */
	if (PageHWPoison(page)) {
		unlock_page(page);
		put_page(page);
		pr_info("soft offline: %#lx page already poisoned\n", pfn);
		return -EBUSY;
	}
	...
}

Thanks
Xishi Qiu













--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] MCE: fix an error of mce_bad_pages statistics

[Borislav Petkov]

On Fri, Dec 07, 2012 at 03:35:15PM +0800, Xishi Qiu wrote:
> Hi Borislav, you mean we should move this to the beginning of soft_offline_page()?
> 
> soft_offline_page()
> {
> 	...
> 	get_any_page()
> 	...
> 	/*
> 	 * Synchronized using the page lock with memory_failure()
> 	 */
> 	if (PageHWPoison(page)) {
> 		unlock_page(page);

Basically yes, except without the unlock_page. Where do you do lock_page
earlier so that you need to unlock it now?

Thanks.

-- 
Regards/Gruss,
    Boris.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>