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

Ryan Roberts
2023-12-04T10:21:45Z

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>
---
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