Re: [PATCH 10/13] mm/vma: convert miscellaneous uses of VMA flags in core mm

On Mon, Jun 29, 2026 at 08:25:33PM +0100, Lorenzo Stoakes wrote:
>Update various uses of legacy flags in vma.c and mmap.c to the new
>vma_flags_t type, updating comments alongside them to be consistent.
>
>Also update __install_special_mapping() to rearrange things slightly to
>accommodate the changes.
>
>Signed-off-by: Lorenzo Stoakes <[email protected]>
>---
[...]
>diff --git a/mm/vma.c b/mm/vma.c
>index b81c05e67a61..ab2ef0f04420 100644
>--- a/mm/vma.c
>+++ b/mm/vma.c
>@@ -3417,23 +3417,27 @@ struct vm_area_struct *__install_special_mapping(
> 	vm_flags_t vm_flags, void *priv,
> 	const struct vm_operations_struct *ops)
> {
>-	int ret;
>+	vma_flags_t vma_flags = legacy_to_vma_flags(vm_flags);
> 	struct vm_area_struct *vma;
>+	int ret;
> 
> 	vma = vm_area_alloc(mm);
>-	if (unlikely(vma == NULL))
>+	if (unlikely(!vma))
> 		return ERR_PTR(-ENOMEM);
> 
>-	vma_set_range(vma, addr, addr + len, 0);
>-	vm_flags |= vma_flags_to_legacy(mm->def_vma_flags) | VM_DONTEXPAND;
>+	vma_flags_set_mask(&vma_flags, mm->def_vma_flags);
>+	vma_flags_set(&vma_flags, VMA_DONTEXPAND_BIT);
> 	if (pgtable_supports_soft_dirty())
>-		vm_flags |= VM_SOFTDIRTY;
>-	vm_flags_init(vma, vm_flags & ~VM_LOCKED_MASK);
>+		vma_flags_set(&vma_flags, VMA_SOFTDIRTY_BIT);
>+	vma_flags_clear_mask(&vma_flags, VMA_LOCKED_MASK);
>+	vma->flags = vma_flags;

Maybe worth a vma_flags_init() helper here to mirror vm_flags_init()?
With this open-coded, we lose the soft-dirty WARN_ON_ONCE sanity check.

Might be nicer to keep that check in one place ;)

[...]