We don't need up-to-date accessed-dirty information for anon folios and can
simply work with the ptent we already have. Also, we know the RSS counter
we want to update.
We can safely move arch_check_zapped_pte() + tlb_remove_tlb_entry() +
zap_install_uffd_wp_if_needed() after updating the folio and RSS.

While at it, only call zap_install_uffd_wp_if_needed() if there is even
any chance that pte_install_uffd_wp_if_needed() would do *something*.
That is, just don't bother if uffd-wp does not apply.

Reviewed-by: Ryan Roberts <ryan.robe...@arm.com>
Signed-off-by: David Hildenbrand <da...@redhat.com>
---
 mm/memory.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 4da6923709b2..7a3ebb6e5909 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1552,12 +1552,9 @@ static inline void zap_present_pte(struct mmu_gather 
*tlb,
        folio = page_folio(page);
        if (unlikely(!should_zap_folio(details, folio)))
                return;
-       ptent = ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm);
-       arch_check_zapped_pte(vma, ptent);
-       tlb_remove_tlb_entry(tlb, pte, addr);
-       zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent);
 
        if (!folio_test_anon(folio)) {
+               ptent = ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm);
                if (pte_dirty(ptent)) {
                        folio_mark_dirty(folio);
                        if (tlb_delay_rmap(tlb)) {
@@ -1567,8 +1564,17 @@ static inline void zap_present_pte(struct mmu_gather 
*tlb,
                }
                if (pte_young(ptent) && likely(vma_has_recency(vma)))
                        folio_mark_accessed(folio);
+               rss[mm_counter(folio)]--;
+       } else {
+               /* We don't need up-to-date accessed/dirty bits. */
+               ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm);
+               rss[MM_ANONPAGES]--;
        }
-       rss[mm_counter(folio)]--;
+       arch_check_zapped_pte(vma, ptent);
+       tlb_remove_tlb_entry(tlb, pte, addr);
+       if (unlikely(userfaultfd_pte_wp(vma, ptent)))
+               zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent);
+
        if (!delay_rmap) {
                folio_remove_rmap_pte(folio, page, vma);
                if (unlikely(page_mapcount(page) < 0))
-- 
2.43.0

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