From bdadc6d83156016d2b5eed582c1458c881c53a1e Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Wed, 21 Jun 2023 17:45:47 +0100 Subject: [PATCH] scatterlist: add sg_set_folio() 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. Link: https://lkml.kernel.org/r/20230621164557.3510324-4-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton --- include/linux/scatterlist.h | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index ec46d8e..77df3d7 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 -- 2.7.4