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-rw-r--r--include/linux/scatterlist.h35
1 files changed, 35 insertions, 0 deletions
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 4bd6c06..788a853 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -231,6 +231,41 @@ size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
*/
#define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
+/*
+ * sg page iterator
+ *
+ * Iterates over sg entries page-by-page. On each successful iteration,
+ * @piter->page points to the current page, @piter->sg to the sg holding this
+ * page and @piter->sg_pgoffset to the page's page offset within the sg. The
+ * iteration will stop either when a maximum number of sg entries was reached
+ * or a terminating sg (sg_last(sg) == true) was reached.
+ */
+struct sg_page_iter {
+ struct page *page; /* current page */
+ struct scatterlist *sg; /* sg holding the page */
+ unsigned int sg_pgoffset; /* page offset within the sg */
+
+ /* these are internal states, keep away */
+ unsigned int __nents; /* remaining sg entries */
+ int __pg_advance; /* nr pages to advance at the
+ * next step */
+};
+
+bool __sg_page_iter_next(struct sg_page_iter *piter);
+void __sg_page_iter_start(struct sg_page_iter *piter,
+ struct scatterlist *sglist, unsigned int nents,
+ unsigned long pgoffset);
+
+/**
+ * for_each_sg_page - iterate over the pages of the given sg list
+ * @sglist: sglist to iterate over
+ * @piter: page iterator to hold current page, sg, sg_pgoffset
+ * @nents: maximum number of sg entries to iterate over
+ * @pgoffset: starting page offset
+ */
+#define for_each_sg_page(sglist, piter, nents, pgoffset) \
+ for (__sg_page_iter_start((piter), (sglist), (nents), (pgoffset)); \
+ __sg_page_iter_next(piter);)
/*
* Mapping sg iterator