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scatterlist: add sg_set_folio()

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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) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2023-06-21 17:45:47 +01:00 committed by Andrew Morton
parent 982a7194af
commit bdadc6d831
1 changed files with 24 additions and 0 deletions
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24
include/linux/scatterlist.h
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@ -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