linux-kernel - Re: [PATCH] mm: rmap: use VM_BUG_ON() in __page_check_anon

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Message-ID: <0d881dbe-b517-a68c-a61f-c4bfe18e75ca@linux.alibaba.com>
Date:   Wed, 6 Nov 2019 09:42:52 -0800
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: rmap: use VM_BUG_ON() in __page_check_anon_rmap()



On 11/6/19 12:28 AM, Kirill A. Shutemov wrote:
> On Wed, Nov 06, 2019 at 01:03:36AM +0800, Yang Shi wrote:
>> The __page_check_anon_rmap() just calls two BUG_ON()s protected by
>> CONFIG_DEBUG_VM, the #ifdef could be eliminated by using VM_BUG_ON().
>>
>> Signed-off-by: Yang Shi <yang.shi@...ux.alibaba.com>
>> ---
>>   mm/rmap.c | 6 ++----
>>   1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/mm/rmap.c b/mm/rmap.c
>> index d17cbf3..39178eb 100644
>> --- a/mm/rmap.c
>> +++ b/mm/rmap.c
>> @@ -1055,7 +1055,6 @@ static void __page_set_anon_rmap(struct page *page,
>>   static void __page_check_anon_rmap(struct page *page,
>>   	struct vm_area_struct *vma, unsigned long address)
>>   {
>> -#ifdef CONFIG_DEBUG_VM
>>   	/*
>>   	 * The page's anon-rmap details (mapping and index) are guaranteed to
>>   	 * be set up correctly at this point.
>> @@ -1068,9 +1067,8 @@ static void __page_check_anon_rmap(struct page *page,
>>   	 * are initially only visible via the pagetables, and the pte is locked
>>   	 * over the call to page_add_new_anon_rmap.
>>   	 */
>> -	BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
>> -	BUG_ON(page_to_pgoff(page) != linear_page_index(vma, address));
>> -#endif
>> +	VM_BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
>> +	VM_BUG_ON(page_to_pgoff(page) != linear_page_index(vma, address));
> Why not VM_BUG_ON_PAGE()?

Because I was not intended to change the behavior, just cleanup. We 
definitely could use VM_BUG_ON_PAGE() if that is preferred.

>