Re: [PATCH 28/39] mm: drop some redundant checks around hugetlb VMAs

[Marc Zyngier]

On Tue, 08 Sep 2026 21:01:32 +0100,
"Lorenzo Stoakes (ARM)" <ljs@xxxxxxxxxx> wrote:
> 
> Adjust code which inadvertently perform redundant checks on hugetlb VMAs
> and clean them up:
> 
> * hugetlb VMAs have VMA_DONTEXPAND_BIT set so a VMA_SPECIAL_FLAGS check
>   suffices. (migrate_vma_setup() regains an explicit hugetlb test later in
>   the series, once VMA_SPECIAL_FLAGS is removed.)
> 
> * hugetlb VMAs unconditionally set vma->vm_ops, so they are never
>   anonymous.
> 
> * hugetlb VMAs do not set VMA_PFNMAP_BIT so checking for this is redundant.
> 
> While we're here also drop a VM_BUG_ON() which the simplified check above
> makes unreachable, and use the new VMA flag API.
> 
> No functional change intended.
> 
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
> ---
>  arch/arm64/kvm/mmu.c         | 4 +---
>  drivers/gpu/drm/drm_gpusvm.c | 3 +--
>  mm/migrate_device.c          | 4 ++--
>  3 files changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index a7968f8d24bf..3c1240ffc38d 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1463,14 +1463,12 @@ static int get_vma_page_shift(struct vm_area_struct *vma, unsigned long hva)
>  {
>  	unsigned long pa;
>  
> -	if (vma_is_hugetlb(vma) && !(vma->vm_flags & VM_PFNMAP))
> +	if (vma_is_hugetlb(vma))
>  		return huge_page_shift(hstate_vma(vma));
>  
>  	if (!(vma->vm_flags & VM_PFNMAP))
>  		return PAGE_SHIFT;
>  
> -	VM_BUG_ON(vma_is_hugetlb(vma));
> -
>  	pa = (vma->vm_pgoff << PAGE_SHIFT) + (hva - vma->vm_start);
>  
>  #ifndef __PAGETABLE_PMD_FOLDED

Acked-by: Marc Zyngier <maz@xxxxxxxxxx>

	M.

-- 
Without deviation from the norm, progress is not possible.