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

[SeongJae Park]

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!


Thanks,
SJ

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