On 7/3/2023 9:53 PM, Ryan Roberts wrote:
> In preparation for FLEXIBLE_THP support, 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
> "small" pages scheme.
>
> Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
Reviewed-by: Yin, Fengwei <fengwei.yin@xxxxxxxxx>
> ---
> mm/rmap.c | 26 +++++++++++++++++++-------
> 1 file changed, 19 insertions(+), 7 deletions(-)
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 1d8369549424..82ef5ba363d1 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1278,31 +1278,43 @@ 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);
> + int i;
> + struct page *page;
>
> - 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);
>
> - if (likely(!folio_test_pmd_mappable(folio))) {
> + if (!folio_test_large(folio)) {
> /* increment count (starts at -1) */
> atomic_set(&folio->_mapcount, 0);
> - nr = 1;
> + __page_set_anon_rmap(folio, &folio->page, vma, address, 1);
> + } else if (!folio_test_pmd_mappable(folio)) {
> + /* increment count (starts at 0) */
> + atomic_set(&folio->_nr_pages_mapped, nr);
> +
> + page = &folio->page;
> + for (i = 0; i < nr; i++, page++, address += PAGE_SIZE) {
> + /* increment count (starts at -1) */
> + atomic_set(&page->_mapcount, 0);
> + __page_set_anon_rmap(folio, page, vma, address, 1);
> + }
> } 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);
> __lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr);
> + __page_set_anon_rmap(folio, &folio->page, vma, address, 1);
> }
>
> __lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr);
> - __page_set_anon_rmap(folio, &folio->page, vma, address, 1);
> }
>
> /**
