Re: [PATCH 2/4] mm/hwpoison: fix miss catch transparent huge page

[Wanpeng Li <liwanp@linux.vnet.ibm.com>]

Hi Naoya,
On Mon, Sep 02, 2013 at 02:34:20PM -0400, Naoya Horiguchi wrote:
>On Mon, Sep 02, 2013 at 08:33:42PM +0800, Wanpeng Li wrote:
>> PageTransHuge() can't guarantee the page is transparent huge page since it 
>> return true for both transparent huge and hugetlbfs pages. This patch fix 
>> it by check the page is also !hugetlbfs page.
>> 
>> Before patch:
>> 
>> [  121.571128] Injecting memory failure at pfn 23a200
>> [  121.571141] MCE 0x23a200: huge page recovery: Delayed
>> [  140.355100] MCE: Memory failure is now running on 0x23a200
>> 
>> After patch:
>> 
>> [   94.290793] Injecting memory failure at pfn 23a000
>> [   94.290800] MCE 0x23a000: huge page recovery: Delayed
>> [  105.722303] MCE: Software-unpoisoned page 0x23a000
>> 
>> Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
>
>PageTransHuge doesn't care about hugetlbfs at all, assuming that it
>shouldn't be called hugetlbfs context as commented.
>
>  /*                                                                    
>   * PageHuge() only returns true for hugetlbfs pages, but not for      
>   * normal or transparent huge pages.                                  
>   *                                                                    
>   * PageTransHuge() returns true for both transparent huge and         
>   * hugetlbfs pages, but not normal pages. PageTransHuge() can only be 
>   * called only in the core VM paths where hugetlbfs pages can't exist.
>   */
>  static inline int PageTransHuge(struct page *page)
>
>I think it's for the ultra optimization of thp, so we can't change that.
>So we need to follow the pattern whenever possible.
>
>  if (PageHuge) {
>    hugetlb specific code
>  } else if (PageTransHuge) {
>    thp specific code
>  }
>  normal page code / common code
>
>> ---
>>  mm/memory-failure.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>> index e28ee77..b114570 100644
>> --- a/mm/memory-failure.c
>> +++ b/mm/memory-failure.c
>> @@ -1349,7 +1349,7 @@ int unpoison_memory(unsigned long pfn)
>>  	 * worked by memory_failure() and the page lock is not held yet.
>>  	 * In such case, we yield to memory_failure() and make unpoison fail.
>>  	 */
>> -	if (PageTransHuge(page)) {
>> +	if (PageTransHuge(page) && !PageHuge(page)) {
>>  		pr_info("MCE: Memory failure is now running on %#lx\n", pfn);
>>  			return 0;
>>  	}
>
>I think that we can effectively follow the above pattern by reversing
>these two checks.

Ok, I will do it this way. 
Btw, thanks for your review the patchset. ;-)

Regards,
Wanpeng Li 

>
>Thanks,
>Naoya Horiguchi

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