[PATCH v1] mm/rmap: use folio->_mapcount for small folios

[David Hildenbrand <david@xxxxxxxxxx>]

We have some cases left whereby we operate on small folios and still
refer to page->_mapcount. Let's just use folio->_mapcount instead, which
currently still overlays page->_mapcount, so no change.

This change will make it easier to later spot any remaining users of
page->_mapcount that target tail pages.

Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
 include/linux/rmap.h | 4 ++--
 mm/rmap.c            | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 07854d1f9ad65..d5e93e44322e5 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -331,7 +331,7 @@ static __always_inline void __folio_dup_file_rmap(struct folio *folio,
 	switch (level) {
 	case RMAP_LEVEL_PTE:
 		if (!folio_test_large(folio)) {
-			atomic_inc(&page->_mapcount);
+			atomic_inc(&folio->_mapcount);
 			break;
 		}
 
@@ -425,7 +425,7 @@ static __always_inline int __folio_try_dup_anon_rmap(struct folio *folio,
 		if (!folio_test_large(folio)) {
 			if (PageAnonExclusive(page))
 				ClearPageAnonExclusive(page);
-			atomic_inc(&page->_mapcount);
+			atomic_inc(&folio->_mapcount);
 			break;
 		}
 
diff --git a/mm/rmap.c b/mm/rmap.c
index 4c330635aa4e7..c09c6c03fc9dc 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1165,7 +1165,7 @@ static __always_inline unsigned int __folio_add_rmap(struct folio *folio,
 	switch (level) {
 	case RMAP_LEVEL_PTE:
 		if (!folio_test_large(folio)) {
-			nr = atomic_inc_and_test(&page->_mapcount);
+			nr = atomic_inc_and_test(&folio->_mapcount);
 			break;
 		}
 
@@ -1535,7 +1535,7 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
 	switch (level) {
 	case RMAP_LEVEL_PTE:
 		if (!folio_test_large(folio)) {
-			nr = atomic_add_negative(-1, &page->_mapcount);
+			nr = atomic_add_negative(-1, &folio->_mapcount);
 			break;
 		}
 
-- 
2.45.2