[PATCH v6 14/27] mm: Add folio_mapcount

Matthew Wilcox (Oracle)
2021-03-31T18:54:40Z

This is the folio equivalent of page_mapcount().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
include/linux/mm.h | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a4f2818aeb1d..fc15a256e686 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -869,6 +869,22 @@ static inline int page_mapcount(struct page *page)
return atomic_read(&page->_mapcount) + 1;
}

+/**
+ * folio_mapcount - The number of mappings of this folio.
+ * @folio: The folio.
+ *
+ * The result includes the number of times any of the pages in the
+ * folio are mapped to userspace.
+ *
+ * Return: The number of page table entries which refer to this folio.
+ */
+static inline int folio_mapcount(struct folio *folio)
+{
+ if (unlikely(FolioMulti(folio)))
+ return __page_mapcount(&folio->page);
+ return atomic_read(&folio->_mapcount) + 1;
+}
+
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
int total_mapcount(struct page *page);
int page_trans_huge_mapcount(struct page *page, int *total_mapcount);
--
2.30.2