Re: [PATCH v8 02/10] mm: Non-pmd-mappable, large folios for folio_add_new_anon_rmap()

Barry Song
2023-12-05T00:58:57Z

On Mon, Dec 4, 2023 at 6:20 PM Ryan Roberts <ryan.roberts@arm.com> wrote:
>
> In preparation for supporting anonymous multi-size THP, improve
> folio_add_new_anon_rmap() to allow a non-pmd-mappable, large folio to be
> passed to it. In this case, all contained pages are accounted using the
> order-0 folio (or base page) scheme.
>
> Reviewed-by: Yu Zhao <yuzhao@google.com>
> Reviewed-by: Yin Fengwei <fengwei.yin@intel.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>

Reviewed-by: Barry Song <v-songbaohua@oppo.com>

> ---
> mm/rmap.c | 28 ++++++++++++++++++++--------
> 1 file changed, 20 insertions(+), 8 deletions(-)
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 2a1e45e6419f..846fc79f3ca9 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1335,32 +1335,44 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
> * This means the inc-and-test can be bypassed.
> * The folio does not have to be locked.
> *
> - * If the folio is large, it is accounted as a THP. As the folio
> + * If the folio is pmd-mappable, it is accounted as a THP. As the folio
> * is new, it's assumed to be mapped exclusively by a single process.
> */
> void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
> unsigned long address)
> {
> - int nr;
> + int nr = folio_nr_pages(folio);
>
> - VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
> + VM_BUG_ON_VMA(address < vma->vm_start ||
> + address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
> __folio_set_swapbacked(folio);
> + __folio_set_anon(folio, vma, address, true);
>
> - if (likely(!folio_test_pmd_mappable(folio))) {
> + if (likely(!folio_test_large(folio))) {
> /* increment count (starts at -1) */
> atomic_set(&folio->_mapcount, 0);
> - nr = 1;
> + SetPageAnonExclusive(&folio->page);
> + } else if (!folio_test_pmd_mappable(folio)) {
> + int i;
> +
> + for (i = 0; i < nr; i++) {
> + struct page *page = folio_page(folio, i);
> +
> + /* increment count (starts at -1) */
> + atomic_set(&page->_mapcount, 0);
> + SetPageAnonExclusive(page);
> + }
> +
> + atomic_set(&folio->_nr_pages_mapped, nr);
> } else {
> /* increment count (starts at -1) */
> atomic_set(&folio->_entire_mapcount, 0);
> atomic_set(&folio->_nr_pages_mapped, COMPOUND_MAPPED);
> - nr = folio_nr_pages(folio);
> + SetPageAnonExclusive(&folio->page);
> __lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr);
> }
>
> __lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr);
> - __folio_set_anon(folio, vma, address, true);
> - SetPageAnonExclusive(&folio->page);
> }
>
> /**
> --
> 2.25.1