[PATCH v1 15/39] mm/huge_memory: batch rmap operations in __split_huge_pmd_locked()

David Hildenbrand
2023-12-11T15:58:13Z

Let's use folio_add_anon_rmap_ptes(), batching the rmap operations.

While at it, use more folio operations (but only in the code branch we're
touching), use VM_WARN_ON_FOLIO(), and pass RMAP_EXCLUSIVE instead of
manually setting PageAnonExclusive.

We should never see non-anon pages on that branch: otherwise, the
existing page_add_anon_rmap() call would have been flawed already.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
mm/huge_memory.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1f5634b2f374..82ad68fe0d12 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2398,6 +2398,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long haddr, bool freeze)
{
struct mm_struct *mm = vma->vm_mm;
+ struct folio *folio;
struct page *page;
pgtable_t pgtable;
pmd_t old_pmd, _pmd;
@@ -2493,16 +2494,18 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
uffd_wp = pmd_swp_uffd_wp(old_pmd);
} else {
page = pmd_page(old_pmd);
+ folio = page_folio(page);
if (pmd_dirty(old_pmd)) {
dirty = true;
- SetPageDirty(page);
+ folio_set_dirty(folio);
}
write = pmd_write(old_pmd);
young = pmd_young(old_pmd);
soft_dirty = pmd_soft_dirty(old_pmd);
uffd_wp = pmd_uffd_wp(old_pmd);

- VM_BUG_ON_PAGE(!page_count(page), page);
+ VM_WARN_ON_FOLIO(!folio_ref_count(folio), folio);
+ VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);

/*
* Without "freeze", we'll simply split the PMD, propagating the
@@ -2519,11 +2522,18 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
*
* See page_try_share_anon_rmap(): invalidate PMD first.
*/
- anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
+ anon_exclusive = PageAnonExclusive(page);
if (freeze && anon_exclusive && page_try_share_anon_rmap(page))
freeze = false;
- if (!freeze)
- page_ref_add(page, HPAGE_PMD_NR - 1);
+ if (!freeze) {
+ rmap_t rmap_flags = RMAP_NONE;
+
+ folio_ref_add(folio, HPAGE_PMD_NR - 1);
+ if (anon_exclusive)
+ rmap_flags |= RMAP_EXCLUSIVE;
+ folio_add_anon_rmap_ptes(folio, page, HPAGE_PMD_NR,
+ vma, haddr, rmap_flags);
+ }
}

/*
@@ -2566,8 +2576,6 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
if (write)
entry = pte_mkwrite(entry, vma);
- if (anon_exclusive)
- SetPageAnonExclusive(page + i);
if (!young)
entry = pte_mkold(entry);
/* NOTE: this may set soft-dirty too on some archs */
@@ -2577,7 +2585,6 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
entry = pte_mksoft_dirty(entry);
if (uffd_wp)
entry = pte_mkuffd_wp(entry);
- page_add_anon_rmap(page + i, vma, addr, RMAP_NONE);
}
VM_BUG_ON(!pte_none(ptep_get(pte)));
set_pte_at(mm, addr, pte, entry);
--
2.43.0