linux-kernel - Re: [PATCH] hugetlbfs: Call VM_BUG_ON_PAGE earlier in free_huge

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Date:   Thu, 29 Nov 2018 12:52:54 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     William Kucharski <william.kucharski@...cle.com>,
        Yongkai Wu <nic.wuyk@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org, nic_w@....com,
        Michal Hocko <mhocko@...nel.org>
Subject: Re: [PATCH] hugetlbfs: Call VM_BUG_ON_PAGE earlier in free_huge_page

On 11/29/18 5:51 AM, William Kucharski wrote:
> Reviewed-by: William Kucharski <william.kucharski@...cle.com>
> 
>> On Nov 29, 2018, at 4:44 AM, Yongkai Wu <nic.wuyk@...il.com> wrote:
>>
>> A stack trace was triggered by VM_BUG_ON_PAGE(page_mapcount(page),
>> page) in free_huge_page().  Unfortunately, the page->mapping field
>> was set to NULL before this test.  This made it more difficult to
>> determine the root cause of the problem.
>>
>> Move the VM_BUG_ON_PAGE tests earlier in the function so that if
>> they do trigger more information is present in the page struct.
>>
>> Signed-off-by: Yongkai Wu <nic_w@....com>
>> Acked-by: Michal Hocko <mhocko@...e.com>
>> Acked-by: Mike Kravetz <mike.kravetz@...cle.com>

Thank you for fixing the formatting and commit message.

Adding Andrew on so he can add to his tree as appropriatre. Also Cc'ing Michal.

>> ---
>> mm/hugetlb.c | 5 +++--
>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index 7f2a28a..14ef274 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -1248,10 +1248,11 @@ void free_huge_page(struct page *page)
>> 		(struct hugepage_subpool *)page_private(page);
>> 	bool restore_reserve;
>>
>> -	set_page_private(page, 0);
>> -	page->mapping = NULL;
>> 	VM_BUG_ON_PAGE(page_count(page), page);
>> 	VM_BUG_ON_PAGE(page_mapcount(page), page);
>> +
>> +	set_page_private(page, 0);
>> +	page->mapping = NULL;
>> 	restore_reserve = PagePrivate(page);
>> 	ClearPagePrivate(page);
>>
>> -- 
>> 1.8.3.1
>>
> 


-- 
Mike Kravetz