Re: [PATCH v2 1/2] mm/mprotect: move softleaf code out of the main function

David Hildenbrand (Arm)
2026-03-24T20:13:07Z

On 3/24/26 16:43, Pedro Falcato wrote:
> Move softleaf change_pte_range code into a separate function. This makes
> the change_pte_range() function a good bit smaller, and lessens cognitive
> load when reading through the function.
>
> Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
> Signed-off-by: Pedro Falcato <pfalcato@suse.de>
> ---
> mm/mprotect.c | 129 +++++++++++++++++++++++++++-----------------------
> 1 file changed, 69 insertions(+), 60 deletions(-)
>
> diff --git a/mm/mprotect.c b/mm/mprotect.c
> index 9681f055b9fc..2eaf862e5734 100644
> --- a/mm/mprotect.c
> +++ b/mm/mprotect.c
> @@ -211,6 +211,74 @@ static void set_write_prot_commit_flush_ptes(struct vm_area_struct *vma,
> commit_anon_folio_batch(vma, folio, page, addr, ptep, oldpte, ptent, nr_ptes, tlb);
> }
>
> +static long change_softleaf_pte(struct vm_area_struct *vma,
> + unsigned long addr, pte_t *pte, pte_t oldpte, unsigned long cp_flags)
> +{
> + const bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
> + const bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;
> + softleaf_t entry = softleaf_from_pte(oldpte);
> + pte_t newpte;
> +
> + if (softleaf_is_migration_write(entry)) {
> + const struct folio *folio = softleaf_to_folio(entry);
> +
> + /*
> + * A protection check is difficult so
> + * just be safe and disable write
> + */
> + if (folio_test_anon(folio))
> + entry = make_readable_exclusive_migration_entry(
> + swp_offset(entry));

We can now even fit this into a single line without feeling bad :)

> + else
> + entry = make_readable_migration_entry(swp_offset(entry));
> + newpte = swp_entry_to_pte(entry);
> + if (pte_swp_soft_dirty(oldpte))
> + newpte = pte_swp_mksoft_dirty(newpte);
> + } else if (softleaf_is_device_private_write(entry)) {
> + /*
> + * We do not preserve soft-dirtiness. See
> + * copy_nonpresent_pte() for explanation.
> + */
> + entry = make_readable_device_private_entry(
> + swp_offset(entry));

Same here.

> + newpte = swp_entry_to_pte(entry);
> + if (pte_swp_uffd_wp(oldpte))
> + newpte = pte_swp_mkuffd_wp(newpte);
> + } else if (softleaf_is_marker(entry)) {
> + /*

Acked-by: David Hildenbrand (Arm) <david@kernel.org>

--
Cheers,

David