Subject: [PATCH 01/10] highmem: Add folio_release_kmap()

From: "Matthew Wilcox (Oracle)" <[email-masked]>
Date: Thu, 21 Sep 2023 00:21:24 -0400

This is the folio equivalent of unmap_and_put_page(), which remains as
a wrapper for it.

Signed-off-by: Matthew Wilcox (Oracle) <[email-masked]>
---
 include/linux/highmem.h | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 99c474de800d..4cacc0e43b51 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -551,10 +551,24 @@ static inline void folio_zero_range(struct folio *folio,
 	zero_user_segments(&folio->page, start, start + length, 0, 0);
 }
 
-static inline void unmap_and_put_page(struct page *page, void *addr)
+/**
+ * folio_release_kmap - Unmap a folio and drop a refcount.
+ * @folio: The folio to release.
+ * @addr: The address previously returned by a call to kmap_local_folio().
+ *
+ * It is common, eg in directory handling to kmap a folio.  This function
+ * unmaps the folio and drops the refcount that was being held to keep the
+ * folio alive while we accessed it.
+ */
+static inline void folio_release_kmap(struct folio *folio, void *addr)
 {
 	kunmap_local(addr);
-	put_page(page);
+	folio_put(folio);
+}
+
+static inline void unmap_and_put_page(struct page *page, void *addr)
+{
+	folio_release_kmap(page_folio(page), addr);
 }
 
 #endif /* _LINUX_HIGHMEM_H */
-- 
2.40.1