Re: [PATCH 03/13] scatterlist: Add sg_set_folio()

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在 2023/6/22 0:45, Matthew Wilcox (Oracle) 写道:
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;
+}
+

https://elixir.bootlin.com/linux/latest/source/lib/scatterlist.c#L451

Does the following function have folio version?

"
int sg_alloc_append_table_from_pages(struct sg_append_table *sgt_append,
		struct page **pages, unsigned int n_pages, unsigned int offset,
		unsigned long size, unsigned int max_segment,
		unsigned int left_pages, gfp_t gfp_mask)
"

Thanks a lot.
Zhu Yanjun

  static inline struct page *sg_page(struct scatterlist *sg)
  {
  #ifdef CONFIG_DEBUG_SG




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