Commit bdadc6d8 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Andrew Morton
Browse files

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: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 982a7194

include/linux/scatterlist.h

+24 −0
Original line number Diff line number Diff line
@@ -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