This wrapper for sg_set_page() lets drivers add folios to a scatterlist
more easily. We could, perhaps, do better by using a different page
in the folio if offset is larger than UINT_MAX, but let's hope we get
a better data structure than this before we need to care about such
large folios.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
include/linux/scatterlist.h | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index ec46d8e8e49d..77df3d7b18a6 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -141,6 +141,30 @@ static inline void sg_set_page(struct scatterlist *sg, struct page *page,
sg->length = len;
}
+/**
+ * sg_set_folio - Set sg entry to point at given folio
+ * @sg: SG entry
+ * @folio: The folio
+ * @len: Length of data
+ * @offset: Offset into folio
+ *
+ * Description:
+ * Use this function to set an sg entry pointing at a folio, never assign
+ * the folio directly. We encode sg table information in the lower bits
+ * of the folio pointer. See sg_page() for looking up the page belonging
+ * to an sg entry.
+ *
+ **/
+static inline void sg_set_folio(struct scatterlist *sg, struct folio *folio,
+ size_t len, size_t offset)
+{
+ WARN_ON_ONCE(len > UINT_MAX);
+ WARN_ON_ONCE(offset > UINT_MAX);
+ sg_assign_page(sg, &folio->page);
+ sg->offset = offset;
+ sg->length = len;
+}
+
static inline struct page *sg_page(struct scatterlist *sg)
{
#ifdef CONFIG_DEBUG_SG
--
2.39.2
