Re: [PATCH v2 1/4] mm: mincore: use walk_page_range_vma() in do_mincore()

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 22 Jun 2026 11:23:11 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> wrote:

> >>>> -	err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec);
> >>>> +
> >>>> +	/*
> >>>> +	 * walk_page_range_vma() does not call walk_page_test(), which
> >>>> +	 * handles VM_PFNMAP VMA by invoking ->pte_hole() to skip the
> >>>> +	 * page table walk. Without this check, PFNMAP PTEs would be
> >>>> +	 * treated as present by mincore_pte_range(), changing the returned
> >>>> +	 * residency status from the historical "not resident" to "resident".
> >>>> +	 * Handle VM_PFNMAP explicitly to preserve the original behavior.
> >>>> +	 */
> > 
> > I would rather we amend this comment to something like:
> > 
> > 	/* mincore (historically) reports PFNMAP mappings as non-resident. */
> > 
> > because we don't need to explain internal differences in walk_page_range
> > functions in a random comment in mincore. And perhaps attempt a separate
> 
> Hope Andrew can fix the comments when pickup patches.

I added this:

--- a/mm/mincore.c~mm-mincore-use-walk_page_range_vma-in-do_mincore-fix
+++ a/mm/mincore.c
@@ -261,12 +261,7 @@ static long do_mincore(unsigned long add
 	}
 
 	/*
-	 * walk_page_range_vma() does not call walk_page_test(), which
-	 * handles VM_PFNMAP VMA by invoking ->pte_hole() to skip the
-	 * page table walk. Without this check, PFNMAP PTEs would be
-	 * treated as present by mincore_pte_range(), changing the returned
-	 * residency status from the historical "not resident" to "resident".
-	 * Handle VM_PFNMAP explicitly to preserve the original behavior.
+	 * mincore historically reports PFNMAP mappings as non-resident.
 	 */
 	if (vma->vm_flags & VM_PFNMAP) {
 		__mincore_unmapped_range(addr, end, vma, vec);
_


Sashiko is OK with your patchset, but it might have found four(!)
pre-existing issues:

	https://sashiko.dev/#/patchset/20260618092845.3905740-1-wangkefeng.wang@huawei.com