Re: [PATCH v3 36/40] mm: avoid use of VMA_SPECIAL_FLAGS in migrate_vma_setup()

[David Hildenbrand (Arm)]

On 9/17/26 18:22, Lorenzo Stoakes (ARM) wrote:
> Now we have the expressive vma_is_kernel_owned() and vma_is_fixed_mapping()
> predicates, use them to determine whether to proceed with migration. This
> drops the VMA_IO_BIT test, which is safe as only kernel-owned mappings may
> set it.
> 
> hugetlb mappings remain excluded, as they are fixed mappings.
> 
> No functional change intended.
> 
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
> ---
>  mm/migrate_device.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/migrate_device.c b/mm/migrate_device.c
> index b9c453c28795..b74c0ae42768 100644
> --- a/mm/migrate_device.c
> +++ b/mm/migrate_device.c
> @@ -739,19 +739,21 @@ static void migrate_vma_unmap(struct migrate_vma *migrate)
>   */
>  int migrate_vma_setup(struct migrate_vma *args)
>  {
> +	const struct vm_area_struct *vma = args->vma;
>  	long nr_pages = (args->end - args->start) >> PAGE_SHIFT;
>  
>  	args->start &= PAGE_MASK;
>  	args->end &= PAGE_MASK;
> -	if (!args->vma || vma_test_any_mask(args->vma, VMA_SPECIAL_FLAGS) ||
> -	    vma_is_dax(args->vma))
> +	if (!vma)
> +		return -EINVAL;
> +	if (vma_is_kernel_owned(vma) || vma_is_fixed_mapping(vma) ||
> +	    vma_is_dax(vma))
>  		return -EINVAL;
>  	if (nr_pages <= 0)
>  		return -EINVAL;
> -	if (args->start < args->vma->vm_start ||
> -	    args->start >= args->vma->vm_end)
> +	if (args->start < vma->vm_start || args->start >= vma->vm_end)
>  		return -EINVAL;
> -	if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end)
> +	if (args->end <= vma->vm_start || args->end > vma->vm_end)
>  		return -EINVAL;
>  	if (!args->src || !args->dst)
>  		return -EINVAL;
> 

Much better, thanks!

Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>

-- 
Cheers,

David