[PATCH 05/48] pagevec: Add folio_batch

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

The folio_batch is the same as the pagevec, except that it is typed
to contain folios and not pages.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/pagevec.h | 63 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/include/linux/pagevec.h b/include/linux/pagevec.h
index 7f3f19065a9f..4483e6ad7607 100644
--- a/include/linux/pagevec.h
+++ b/include/linux/pagevec.h
@@ -15,6 +15,7 @@
 #define PAGEVEC_SIZE	15
 
 struct page;
+struct folio;
 struct address_space;
 
 struct pagevec {
@@ -81,4 +82,66 @@ static inline void pagevec_release(struct pagevec *pvec)
 		__pagevec_release(pvec);
 }
 
+/**
+ * struct folio_batch - A collection of folios.
+ *
+ * The folio_batch is used to amortise the cost of retrieving and
+ * operating on a set of folios.  The order of folios in the batch is
+ * not considered important.  Some users of the folio_batch store
+ * "exceptional" entries in it which can be removed by calling
+ * folio_batch_remove_exceptionals().
+ */
+struct folio_batch {
+	unsigned char nr;
+	unsigned char aux[3];
+	struct folio *folios[PAGEVEC_SIZE];
+};
+
+/**
+ * folio_batch_init() - Initialise a batch of folios
+ * @fbatch: The folio batch.
+ *
+ * A freshly initialised folio_batch contains zero folios.
+ */
+static inline void folio_batch_init(struct folio_batch *fbatch)
+{
+	fbatch->nr = 0;
+}
+
+static inline unsigned int folio_batch_count(struct folio_batch *fbatch)
+{
+	return fbatch->nr;
+}
+
+static inline unsigned int fbatch_space(struct folio_batch *fbatch)
+{
+	return PAGEVEC_SIZE - fbatch->nr;
+}
+
+/**
+ * folio_batch_add() - Add a folio to a batch.
+ * @fbatch: The folio batch.
+ * @folio: The folio to add.
+ *
+ * The folio is added to the end of the batch.
+ * The batch must have previously been initialised using folio_batch_init().
+ *
+ * Return: The number of slots still available.
+ */
+static inline unsigned folio_batch_add(struct folio_batch *fbatch,
+		struct folio *folio)
+{
+	fbatch->folios[fbatch->nr++] = folio;
+	return fbatch_space(fbatch);
+}
+
+static inline void folio_batch_release(struct folio_batch *fbatch)
+{
+	pagevec_release((struct pagevec *)fbatch);
+}
+
+static inline void folio_batch_remove_exceptionals(struct folio_batch *fbatch)
+{
+	pagevec_remove_exceptionals((struct pagevec *)fbatch);
+}
 #endif /* _LINUX_PAGEVEC_H */
-- 
2.33.0