* [PATCH] mm/khugepaged: use round_{up,down}() for PMD alignment in madvise_collapse()
@ 2026-04-08 9:35 Ye Liu
2026-04-08 10:34 ` David Hildenbrand (Arm)
0 siblings, 1 reply; 2+ messages in thread
From: Ye Liu @ 2026-04-08 9:35 UTC (permalink / raw)
To: Andrew Morton, David Hildenbrand, Lorenzo Stoakes
Cc: Ye Liu, Zi Yan, Baolin Wang, Liam R. Howlett, Nico Pache,
Ryan Roberts, Dev Jain, Barry Song, Lance Yang, linux-mm,
linux-kernel
From: Ye Liu <liuye@kylinos.cn>
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@kylinos.cn>
---
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;
--
2.43.0
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] mm/khugepaged: use round_{up,down}() for PMD alignment in madvise_collapse()
2026-04-08 9:35 [PATCH] mm/khugepaged: use round_{up,down}() for PMD alignment in madvise_collapse() Ye Liu
@ 2026-04-08 10:34 ` David Hildenbrand (Arm)
0 siblings, 0 replies; 2+ messages in thread
From: David Hildenbrand (Arm) @ 2026-04-08 10:34 UTC (permalink / raw)
To: Ye Liu, Andrew Morton, Lorenzo Stoakes
Cc: Ye Liu, Zi Yan, Baolin Wang, Liam R. Howlett, Nico Pache,
Ryan Roberts, Dev Jain, Barry Song, Lance Yang, linux-mm,
linux-kernel
On 4/8/26 11:35, Ye Liu wrote:
> From: Ye Liu <liuye@kylinos.cn>
>
> 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@kylinos.cn>
> ---
> 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
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