Re: [PATCH 2/6] fs/proc/task_mmu: use huge_page_size() in pagemap_scan_hugetlb_entry()

[Lorenzo Stoakes]

On Fri, May 29, 2026 at 06:23:26PM +0100, Kiryl Shutsemau (Meta) wrote:
> The partial-page check compares against HPAGE_SIZE (PMD_SIZE), which
> is wrong for gigantic hugetlb hstates (e.g. 1G). The walker hands the
> callback a huge_page_size()-sized range, never start + HPAGE_SIZE, so
> the comparison always declares it partial and aborts the WP. Compare
> against the actual hstate's page size.
>
> Fixes: 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs")
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: Sashiko AI review <sashiko-bot@xxxxxxxxxx>
> Signed-off-by: Kiryl Shutsemau <kas@xxxxxxxxxx>

LGTM, so:

Reviewed-by: Lorenzo Stoakes <ljs@xxxxxxxxxx>

> ---
>  fs/proc/task_mmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index e21a38ac745b..1489c67e88f7 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -2960,7 +2960,7 @@ static int pagemap_scan_hugetlb_entry(pte_t *ptep, unsigned long hmask,
>  	if (~categories & PAGE_IS_WRITTEN)
>  		goto out_unlock;
>
> -	if (end != start + HPAGE_SIZE) {
> +	if (end != start + huge_page_size(hstate_vma(vma))) {
>  		/* Partial HugeTLB page WP isn't possible. */
>  		pagemap_scan_backout_range(p, start, end);
>  		p->arg.walk_end = start;
> --
> 2.54.0
>