On Mon, Oct 2, 2023 at 7:29 AM David Hildenbrand <david@xxxxxxxxxx> wrote:
>
> Let's move it into the caller: there is a difference between whether an
> anon folio can only be mapped by one process (e.g., into one VMA), and
> whether it is truly exclusive (e.g., no references -- including GUP --
> from other processes).
>
> Further, for large folios the page might not actually be pointing at the
> head page of the folio, so it better be handled in the caller. This is a
> preparation for converting page_move_anon_rmap() to consume a folio.
>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> ---
> mm/huge_memory.c | 1 +
> mm/hugetlb.c | 4 +++-
> mm/memory.c | 1 +
> mm/rmap.c | 1 -
> 4 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index e54fb9c542bb..01d0d65ece13 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1506,6 +1506,7 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf)
> pmd_t entry;
>
> page_move_anon_rmap(page, vma);
> + SetPageAnonExclusive(page);
> folio_unlock(folio);
> reuse:
> if (unlikely(unshare)) {
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 9c22297d9c57..24591fc145ff 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -5460,8 +5460,10 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma,
> * owner and can reuse this page.
> */
> if (folio_mapcount(old_folio) == 1 && folio_test_anon(old_folio)) {
> - if (!PageAnonExclusive(&old_folio->page))
> + if (!PageAnonExclusive(&old_folio->page)) {
> page_move_anon_rmap(&old_folio->page, vma);
> + SetPageAnonExclusive(&old_folio->page);
> + }
> if (likely(!unshare))
> set_huge_ptep_writable(vma, haddr, ptep);
>
> diff --git a/mm/memory.c b/mm/memory.c
> index d4820802b01b..9de231c92769 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3484,6 +3484,7 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf)
> * sunglasses. Hit it.
> */
> page_move_anon_rmap(vmf->page, vma);
> + SetPageAnonExclusive(vmf->page);
> folio_unlock(folio);
> reuse:
> if (unlikely(unshare)) {
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 77222adccda1..854ccbd66954 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1165,7 +1165,6 @@ void page_move_anon_rmap(struct page *page, struct vm_area_struct *vma)
> * folio_test_anon()) will not see one without the other.
> */
> WRITE_ONCE(folio->mapping, anon_vma);
> - SetPageAnonExclusive(page);
> }
>
> /**
> --
> 2.41.0
>
