Add a function, folio_change_private(), that will change the private data
attached to a folio, without the need to twiddle the private bit or the
refcount. It assumes that folio_add_private() has already been called on
the page.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
include/linux/pagemap.h | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index f55d8d9001a9..c8d336e62177 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -229,6 +229,25 @@ static inline void folio_attach_private(struct folio *folio, void *data)
folio_set_private(folio);
}
+/**
+ * folio_change_private - Change private data on a folio.
+ * @folio: Folio to change the data on.
+ * @data: Data to set on the folio.
+ *
+ * Change the private data attached to a folio and return the old
+ * data. The page must previously have had data attached and the data
+ * must be detached before the folio will be freed.
+ *
+ * Return: Data that was previously attached to the folio.
+ */
+static inline void *folio_change_private(struct folio *folio, void *data)
+{
+ void *old = folio_get_private(folio);
+
+ folio->private = data;
+ return old;
+}
+
/**
* folio_detach_private - Detach private data from a folio.
* @folio: Folio to detach data from.
