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

["David Hildenbrand (Arm)" <david@kernel.org>]

On 6/18/26 13:49, Pedro Falcato wrote:
> Please CC reviewers properly!
> 
> On Thu, Jun 18, 2026 at 05:28:42PM +0800, Kefeng Wang wrote:
>> The do_mincore() uses walk_page_range() to walk the page table.
>> Fortunately, the caller always passes start/end that falls within
>> a single VMA, so it's safe to use the walk_page_range_vma() in
>> do_mincore() to eliminate an unnecessary find_vma() lookup.
>>
>> Unlike walk_page_range(), walk_page_range_vma() does not call
>> walk_page_test(), which handles VM_PFNMAP by invoking ->pte_hole()
> 
> Why not? Can we fix that instead? I really don't like having this open
> coded in callers. Are there callers of walk_page_range_vma() that expect
> to look at PFNMAP mappings as well? From what I can see, the callers all
> seem to operate on folios (and/or anonymous memory).

I'd rather not.

commit c31783eeae7b22dc3f6edde7339de6112959225d
Author: David Hildenbrand <david@kernel.org>
Date:   Fri Oct 21 12:11:38 2022 +0200

    mm/pagewalk: don't trigger test_walk() in walk_page_vma()

    As Peter points out, the caller passes a single VMA and can just do that
    check itself.

    And in fact, no existing users rely on test_walk() getting called.  So
    let's just remove it and make the implementation slightly more efficient.


-- 
Cheers,

David