Re: [PATCH 05/13] mm: convert THP VMA flag tests to use vma_flags_t

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

On 11/5/26 22:30, Lorenzo Stoakes (ARM) wrote:
> Replace use of the legacy vm_flags_t flags with vma_flags_t values where
> VMA flags are tested directly in the THP and khugepaged logic.
> 
> The thp_vma_allowable_orders() family of functions, hugepage_madvise() and
> khugepaged_enter_vma() continue to take legacy flags for the time being.
> 
> Also update BUG_ON()'s to VM_WARN_ON_ONCE() while here.
> 
> No functional change intended.
> 
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
> ---
>  mm/huge_memory.c | 32 ++++++++++++++++----------------
>  mm/khugepaged.c  |  8 +++++---
>  2 files changed, 21 insertions(+), 19 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 7e589a2fb02d..764e693b422f 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1257,7 +1257,7 @@ __setup("thp_anon=", setup_thp_anon);
>  
>  pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
>  {
> -	if (likely(vma->vm_flags & VM_WRITE))
> +	if (likely(vma_test(vma, VMA_WRITE_BIT)))
>  		pmd = pmd_mkwrite(pmd, vma);
>  	return pmd;
>  }
> @@ -1517,7 +1517,7 @@ vm_fault_t do_huge_pmd_device_private(struct vm_fault *vmf)
>   */
>  gfp_t vma_thp_gfp_mask(struct vm_area_struct *vma)
>  {
> -	const bool vma_madvised = vma && (vma->vm_flags & VM_HUGEPAGE);
> +	const bool vma_madvised = vma && vma_test(vma, VMA_HUGEPAGE_BIT);
>  
>  	/* Always do synchronous compaction */
>  	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
> @@ -1716,10 +1716,9 @@ vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, unsigned long pfn,
>  	 * but we need to be consistent with PTEs and architectures that
>  	 * can't support a 'special' bit.
>  	 */
> -	BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
> -	BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
> -						(VM_PFNMAP|VM_MIXEDMAP));
> -	BUG_ON((vma->vm_flags & VM_PFNMAP) && vma_is_cow_mapping(vma));
> +	VM_WARN_ON_ONCE(!vma_test_any(vma, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT));
> +	VM_WARN_ON_ONCE(vma_test_all(vma, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT));
> +	VM_WARN_ON_ONCE(vma_test(vma, VMA_PFNMAP_BIT) && vma_is_cow_mapping(vma));
>  
>  	if (unlikely(is_huge_zero_pfn(pfn)))
>  		return VM_FAULT_SIGBUS;
> @@ -1750,7 +1749,7 @@ EXPORT_SYMBOL_GPL(vmf_insert_folio_pmd);
>  #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
>  static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
>  {
> -	if (likely(vma->vm_flags & VM_WRITE))
> +	if (likely(vma_test(vma, VMA_WRITE_BIT)))
>  		pud = pud_mkwrite(pud);
>  	return pud;
>  }
> @@ -1827,10 +1826,9 @@ vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, unsigned long pfn,
>  	 * but we need to be consistent with PTEs and architectures that
>  	 * can't support a 'special' bit.
>  	 */
> -	BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
> -	BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
> -						(VM_PFNMAP|VM_MIXEDMAP));
> -	BUG_ON((vma->vm_flags & VM_PFNMAP) && vma_is_cow_mapping(vma));
> +	VM_WARN_ON_ONCE(!vma_test_any(vma, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT));
> +	VM_WARN_ON_ONCE(vma_test_all(vma, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT));
> +	VM_WARN_ON_ONCE(vma_test(vma, VMA_PFNMAP_BIT) && vma_is_cow_mapping(vma));
>  
>  	pfnmap_setup_cachemode_pfn(pfn, &pgprot);
>  
> @@ -2262,7 +2260,7 @@ static inline bool can_change_pmd_writable(struct vm_area_struct *vma,
>  {
>  	struct page *page;
>  
> -	if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE)))
> +	if (WARN_ON_ONCE(!vma_test(vma, VMA_WRITE_BIT)))
>  		return false;
>  
>  	/* Don't touch entries that are not even readable (NUMA hinting). */
> @@ -2277,7 +2275,7 @@ static inline bool can_change_pmd_writable(struct vm_area_struct *vma,
>  	if (userfaultfd_huge_pmd_wp(vma, pmd))
>  		return false;
>  
> -	if (!(vma->vm_flags & VM_SHARED)) {
> +	if (!vma_test(vma, VMA_SHARED_BIT)) {
>  		/* See can_change_pte_writable(). */
>  		page = vm_normal_page_pmd(vma, addr, pmd);
>  		return page && PageAnon(page) && PageAnonExclusive(page);
> @@ -3568,7 +3566,8 @@ static bool __discard_anon_folio_pmd_locked(struct vm_area_struct *vma,
>  
>  	if (pmd_dirty(orig_pmd))
>  		folio_set_dirty(folio);
> -	if (folio_test_dirty(folio) && !(vma->vm_flags & VM_DROPPABLE)) {
> +	if (folio_test_dirty(folio) &&
> +	    !vma_test_single_mask(vma, VMA_DROPPABLE)) {
>  		folio_set_swapbacked(folio);
>  		return false;
>  	}
> @@ -3600,7 +3599,8 @@ static bool __discard_anon_folio_pmd_locked(struct vm_area_struct *vma,
>  	 */
>  	if (pmd_dirty(orig_pmd))
>  		folio_set_dirty(folio);
> -	if (folio_test_dirty(folio) && !(vma->vm_flags & VM_DROPPABLE)) {
> +	if (folio_test_dirty(folio) &&
> +	    !vma_test_single_mask(vma, VMA_DROPPABLE)) {
>  		folio_set_swapbacked(folio);
>  		set_pmd_at(mm, addr, pmdp, orig_pmd);
>  		return false;
> @@ -3614,7 +3614,7 @@ static bool __discard_anon_folio_pmd_locked(struct vm_area_struct *vma,
>  	folio_remove_rmap_pmd(folio, pmd_page(orig_pmd), vma);
>  	zap_deposited_table(mm, pmdp);
>  	add_mm_counter(mm, MM_ANONPAGES, -HPAGE_PMD_NR);
> -	if (vma->vm_flags & VM_LOCKED)
> +	if (vma_test(vma, VMA_LOCKED_BIT))
>  		mlock_drain_local();
>  	folio_put(folio);
>  
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 0d3bd9e23613..a2c7c6a0768d 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -640,7 +640,8 @@ static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma,
>  		 * If the vma has the VM_DROPPABLE flag, the collapse will
>  		 * preserve the lazyfree property without needing to skip.
>  		 */
> -		if (cc->policy.anon_skip_lazyfree && !(vma->vm_flags & VM_DROPPABLE) &&
> +		if (cc->policy.anon_skip_lazyfree &&
> +		    !vma_test_single_mask(vma, VMA_DROPPABLE) &&
>  		    folio_test_lazyfree(folio) && !pte_dirty(pteval)) {
>  			result = SCAN_PAGE_LAZYFREE;
>  			goto out;
> @@ -1683,7 +1684,8 @@ static enum scan_result collapse_scan_anon(struct vm_area_struct *vma,
>  		 * If the vma has the VM_DROPPABLE flag, the collapse will
>  		 * preserve the lazyfree property without needing to skip.
>  		 */
> -		if (cc->policy.anon_skip_lazyfree && !(vma->vm_flags & VM_DROPPABLE) &&
> +		if (cc->policy.anon_skip_lazyfree &&
> +		    !vma_test_single_mask(vma, VMA_DROPPABLE) &&
>  		    folio_test_lazyfree(folio) && !pte_dirty(pteval)) {
>  			result = SCAN_PAGE_LAZYFREE;
>  			failed_pfn = folio_pfn(folio);
> @@ -1948,7 +1950,7 @@ static enum scan_result try_collapse_pte_mapped_thp(struct mm_struct *mm, unsign
>  	 * So page lock of folio does not protect from it, so we must not drop
>  	 * ptl before pgt_pmd is removed, so uffd private needs pml taken now.
>  	 */
> -	if (userfaultfd_armed(vma) && !(vma->vm_flags & VM_SHARED))
> +	if (userfaultfd_armed(vma) && !vma_test(vma, VMA_SHARED_BIT))
>  		pml = pmd_lock(mm, pmd);

A patch in mm/core.git will remove that entirely.

Right now it results in a conflict between mm-new and mm/core.git.

Beat to drop this here entirely. (I can also drop it when applying)

-- 
Cheers,

David