Re: [PATCH v5 34/38] mm: eliminate VMA_SPECIAL_FLAGS check in lru_gen_look_around()

[David Hildenbrand (Arm)]

On 10/9/26 20:04, Lorenzo Stoakes (ARM) wrote:
> A fixed or non-mm-managed mapping is one which sets VMA_PFNMAP_BIT,
> VMA_MIXEDMAP_BIT or VMA_DONTEXPAND_BIT, which is precisely what
> VMA_SPECIAL_FLAGS tests for other than VMA_IO_BIT, which is safe to drop as
> mm-managed mappings may not set it.
> 
> Using these predicates rather than VMA_SPECIAL_FLAGS makes the check
> self-documenting and helps eliminate the confusion around 'special' flags.
> 
> No functional change intended.
> 
> Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
> Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
> ---
>  mm/vmscan.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 3b318efa2916..7adffe8182b3 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -4418,8 +4418,8 @@ bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw, unsigned int nr)
>  	if (spin_is_contended(pvmw->ptl))
>  		return true;
>  
> -	/* exclude special VMAs containing anon pages from COW */
> -	if (vma->vm_flags & VM_SPECIAL)
> +	/* exclude fixed and non-mm-managed VMAs containing anon pages from COW */
> +	if (!vma_is_mm_managed(vma) || vma_is_fixed_mapping(vma))
>  		return true;

If you keep the droppable thing out there you can just use

vma_is_mm_backed() here I think.

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

-- 
Cheers,

David