[PATCH v1 3/9] mm/memory: further separate anon and pagecache folio handling in zap_present_pte()

David Hildenbrand
2024-01-29T14:32:48Z

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.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
mm/memory.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 69502cdc0a7d..20bc13ab8db2 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