[PATCH 39/75] mm: Add folio_pgoff()

[Matthew Wilcox (Oracle)]

This is the folio equivalent of page_to_pgoff().

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 include/linux/pagemap.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index cdb3f118603a..dddd660da24f 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -703,6 +703,17 @@ static inline loff_t folio_file_pos(struct folio *folio)
 	return page_file_offset(&folio->page);
 }
 
+/*
+ * Get the offset in PAGE_SIZE (even for hugetlb folios).
+ * (TODO: hugetlb folios should have ->index in PAGE_SIZE)
+ */
+static inline pgoff_t folio_pgoff(struct folio *folio)
+{
+	if (unlikely(folio_test_hugetlb(folio)))
+		return hugetlb_basepage_index(&folio->page);
+	return folio->index;
+}
+
 extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
 				     unsigned long address);
 
-- 
2.34.1