diff options
Diffstat (limited to 'include/linux/scatterlist.h')
| -rw-r--r-- | include/linux/scatterlist.h | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 4bd6c06eb28e..788a853aa7a7 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 |