[PATCH 2/8] iov_iter: add iovec_nr_user_vecs() helper

[Jens Axboe <axboe@kernel.dk>]

This returns the number of user segments in an iov_iter. The input can
either be an ITER_IOVEC, where it'll return the number of iovecs. Or it
can be an ITER_UBUF, in which case the number of segments is always 1.

Outside of those two, no user backed iterators exist. Just return 0 for
those.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 include/linux/uio.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 3b4403efcce1..8ba4d61e9e9b 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -168,6 +168,15 @@ static inline struct iovec iov_iter_iovec(const struct iov_iter *iter)
 	}
 }
 
+static inline int iovec_nr_user_vecs(const struct iov_iter *iter)
+{
+	if (iter_is_ubuf(iter))
+		return 1;
+	else if (iter->iter_type == ITER_IOVEC)
+		return iter->nr_segs;
+	return 0;
+}
+
 size_t copy_page_from_iter_atomic(struct page *page, unsigned offset,
 				  size_t bytes, struct iov_iter *i);
 void iov_iter_advance(struct iov_iter *i, size_t bytes);
-- 
2.39.2