Re: [PATCH v3 14/16] mm: remove is_hugetlb_entry_[migration, hwpoisoned]()

Vlastimil Babka
2025-11-27T17:29:43Z

On 11/10/25 23:21, Lorenzo Stoakes wrote:
> We do not need to have explicit helper functions for these, it adds a level
> of confusion and indirection when we can simply use software leaf entry
> logic here instead and spell out the special huge_pte_none() case we must
> consider.
>
> No functional change intended.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

Reviewed-by: Vlastimil Babka <vbabka@suse.cz>

But seems to me a fixup is needed:

> ---
> fs/proc/task_mmu.c | 19 +++++----
> include/linux/hugetlb.h | 2 -
> mm/hugetlb.c | 91 +++++++++++++++++------------------------
> mm/mempolicy.c | 17 +++++---
> mm/migrate.c | 15 +++++--
> 5 files changed, 69 insertions(+), 75 deletions(-)
>
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 6cb9e1691e18..3cdefa7546db 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -2499,22 +2499,23 @@ static void make_uffd_wp_huge_pte(struct vm_area_struct *vma,
> unsigned long addr, pte_t *ptep,
> pte_t ptent)
> {
> - unsigned long psize;
> + const unsigned long psize = huge_page_size(hstate_vma(vma));
> + softleaf_t entry;
>
> - if (is_hugetlb_entry_hwpoisoned(ptent) || pte_is_marker(ptent))
> - return;
> + if (huge_pte_none(ptent))
> + set_huge_pte_at(vma->vm_mm, addr, ptep,
> + make_pte_marker(PTE_MARKER_UFFD_WP), psize);

Shouldn't we return here? Otherwise AFAICS we'll also reach the
huge_ptep_modify_prot_commit() below and that wasn't happening before.

>
> - psize = huge_page_size(hstate_vma(vma));
> + entry = softleaf_from_pte(ptent);
> + if (softleaf_is_hwpoison(entry) || softleaf_is_marker(entry))
> + return;
>
> - if (is_hugetlb_entry_migration(ptent))
> + if (softleaf_is_migration(entry))
> set_huge_pte_at(vma->vm_mm, addr, ptep,
> pte_swp_mkuffd_wp(ptent), psize);
> - else if (!huge_pte_none(ptent))
> + else
> huge_ptep_modify_prot_commit(vma, addr, ptep, ptent,
> huge_pte_mkuffd_wp(ptent));
> - else
> - set_huge_pte_at(vma->vm_mm, addr, ptep,
> - make_pte_marker(PTE_MARKER_UFFD_WP), psize);
> }
> #endif /* CONFIG_HUGETLB_PAGE */
>