Re: [PATCH] mm/khugepaged: use round_{up,down}() for PMD alignment in madvise_collapse()

[David Hildenbrand (Arm)]

On 4/8/26 11:35, Ye Liu wrote:
> From: Ye Liu <liuye@xxxxxxxxxx>
> 
> The PMD alignment in madvise_collapse() is currently implemented
> using open-coded bitmask operations:
> 
>     (start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK
>     end & HPAGE_PMD_MASK
> 
> Replace them with round_up() and round_down(), which express the
> same alignment semantics more directly and match other PMD-alignment
> code paths in khugepaged.
> 
> No functional change intended.
> 
> Signed-off-by: Ye Liu <liuye@xxxxxxxxxx>
> ---
>  mm/khugepaged.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 1e2bff40d014..80d0b7136b58 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -2835,8 +2835,8 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start,
>  	mmgrab(mm);
>  	lru_add_drain_all();
>  
> -	hstart = (start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
> -	hend = end & HPAGE_PMD_MASK;
> +	hstart = round_up(start, HPAGE_PMD_SIZE);
> +	hend = round_down(end, HPAGE_PMD_SIZE);
>  
>  	for (addr = hstart; addr < hend; addr += HPAGE_PMD_SIZE) {
>  		enum scan_result result = SCAN_FAIL;

I tend to prefer ALIGN / ALIGN_DOWN when dealing with sizes + addresses.

-- 
Cheers,

David