Subject: Re: [PATCH 3/5] mm/mremap: use pmd_addr_end to calculate next in move_page_tables()

From: Wei Yang <[email-masked]>
Date: Tue, 28 Jan 2020 08:43:01 +0800

On Sun, Jan 26, 2020 at 05:47:57PM +0300, Dmitry Osipenko wrote:
>18.01.2020 02:22, Wei Yang пишет:
>> Use the general helper instead of do it by hand.
>> 
>> Signed-off-by: Wei Yang <[email-masked]>
>> ---
>>  mm/mremap.c | 7 ++-----
>>  1 file changed, 2 insertions(+), 5 deletions(-)
>> 
>> diff --git a/mm/mremap.c b/mm/mremap.c
>> index c2af8ba4ba43..a258914f3ee1 100644
>> --- a/mm/mremap.c
>> +++ b/mm/mremap.c
>> @@ -253,11 +253,8 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
>>  
>>  	for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
>>  		cond_resched();
>> -		next = (old_addr + PMD_SIZE) & PMD_MASK;
>> -		/* even if next overflowed, extent below will be ok */
>> +		next = pmd_addr_end(old_addr, old_end);
>>  		extent = next - old_addr;
>> -		if (extent > old_end - old_addr)
>> -			extent = old_end - old_addr;
>>  		old_pmd = get_old_pmd(vma->vm_mm, old_addr);
>>  		if (!old_pmd)
>>  			continue;
>> @@ -301,7 +298,7 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
>>  
>>  		if (pte_alloc(new_vma->vm_mm, new_pmd))
>>  			break;
>> -		next = (new_addr + PMD_SIZE) & PMD_MASK;
>> +		next = pmd_addr_end(new_addr, new_addr + len);
>>  		if (extent > next - new_addr)
>>  			extent = next - new_addr;
>>  		move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma,
>> 
>
>Hello Wei,
>
>Starting with next-20200122, I'm seeing the following in KMSG on NVIDIA
>Tegra (ARM32):
>
>  BUG: Bad rss-counter state mm:(ptrval) type:MM_ANONPAGES val:190
>

Thanks.

Would you mind letting me know which case you are testing? Or the special
thing is 32-bit platform?

>and eventually kernel hangs.
>
>Git's bisection points to this patch and reverting it helps. Please fix,
>thanks in advance.

-- 
Wei Yang
Help you, Help me

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