Re: [PATCH] mm/migrate_device: Cleanup up PMD Checks and warnings

[David Hildenbrand (Arm)]

On 4/17/26 01:52, SeongJae Park wrote:
> On Thu, 16 Apr 2026 21:44:15 +0200 "David Hildenbrand (Arm)" <david@xxxxxxxxxx> wrote:
> 
>> On 4/14/26 16:13, Sunny Patel wrote:
> [...]
>>> @@ -865,12 +864,13 @@ static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate,
>>>  	if (userfaultfd_missing(vma))
>>>  		goto unlock_abort;
>>>  
>>> -	if (!pmd_none(*pmdp)) {
>>> +	if (pmd_present(*pmdp)) {
>>>  		if (!is_huge_zero_pmd(*pmdp))
>>>  			goto unlock_abort;
>>>  		flush = true;
>>> -	} else if (!pmd_none(*pmdp))
>>> +	} else if (!pmd_none(*pmdp)) {
>>>  		goto unlock_abort;
>>> +	}
>>>  
>>>  	add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
>>>  	folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE);
>>
>> is_huge_zero_pmd() checks pmd_present(), so we didn't have a bug before.
>>
>> We could also do:
>>
>> if (is_huge_zero_pmd(*pmdp)) {
>> 	flush = true;
>> } else if (!pmd_none(*pmdp)) {
>> 	goto unlock_abort;
>> }
> 
> Then we could even further remove the braces and reduce one more line, nice!

Indeed :)

-- 
Cheers,

David