diff options
| -rw-r--r-- | block/bio.c | 49 | ||||
| -rw-r--r-- | include/linux/bio.h | 1 |
2 files changed, 50 insertions, 0 deletions
diff --git a/block/bio.c b/block/bio.c index db85c5753a76..2cf6ebabc68c 100644 --- a/block/bio.c +++ b/block/bio.c @@ -847,6 +847,55 @@ done: } EXPORT_SYMBOL(bio_add_page); +/** + * bio_iov_iter_get_pages - pin user or kernel pages and add them to a bio + * @bio: bio to add pages to + * @iter: iov iterator describing the region to be mapped + * + * Pins as many pages from *iter and appends them to @bio's bvec array. The + * pages will have to be released using put_page() when done. + */ +int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) +{ + unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt; + struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt; + struct page **pages = (struct page **)bv; + size_t offset, diff; + ssize_t size; + + size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset); + if (unlikely(size <= 0)) + return size ? size : -EFAULT; + nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE; + + /* + * Deep magic below: We need to walk the pinned pages backwards + * because we are abusing the space allocated for the bio_vecs + * for the page array. Because the bio_vecs are larger than the + * page pointers by definition this will always work. But it also + * means we can't use bio_add_page, so any changes to it's semantics + * need to be reflected here as well. + */ + bio->bi_iter.bi_size += size; + bio->bi_vcnt += nr_pages; + + diff = (nr_pages * PAGE_SIZE - offset) - size; + while (nr_pages--) { + bv[nr_pages].bv_page = pages[nr_pages]; + bv[nr_pages].bv_len = PAGE_SIZE; + bv[nr_pages].bv_offset = 0; + } + + bv[0].bv_offset += offset; + bv[0].bv_len -= offset; + if (diff) + bv[bio->bi_vcnt - 1].bv_len -= diff; + + iov_iter_advance(iter, size); + return 0; +} +EXPORT_SYMBOL_GPL(bio_iov_iter_get_pages); + struct submit_bio_ret { struct completion event; int error; diff --git a/include/linux/bio.h b/include/linux/bio.h index 5c604b4914bf..d367cd37a7f7 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -427,6 +427,7 @@ void bio_chain(struct bio *, struct bio *); extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int); extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *, unsigned int, unsigned int); +int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter); struct rq_map_data; extern struct bio *bio_map_user_iov(struct request_queue *, const struct iov_iter *, gfp_t); |