Re: [PATCH v4 06/14] vringh: add vringh_kiov_length() helper

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On Mon, Mar 15, 2021 at 05:51:30PM +0100, Laurent Vivier wrote:
On 15/03/2021 17:34, Stefano Garzarella wrote:
This new helper returns the total number of bytes covered by
a vringh_kiov.

Suggested-by: Jason Wang <jasowang@xxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
---
 include/linux/vringh.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/vringh.h b/include/linux/vringh.h
index 755211ebd195..84db7b8f912f 100644
--- a/include/linux/vringh.h
+++ b/include/linux/vringh.h
@@ -199,6 +199,17 @@ static inline void vringh_kiov_cleanup(struct vringh_kiov *kiov)
 	kiov->iov = NULL;
 }

+static inline size_t vringh_kiov_length(struct vringh_kiov *kiov)
+{
+	size_t len = 0;
+	int i;
+
+	for (i = kiov->i; i < kiov->used; i++)
+		len += kiov->iov[i].iov_len;
+
+	return len;
+}

Do we really need an helper?

For instance, we can use:

len = iov_length((struct iovec *)kiov->iov, kiov->used);

Or do we want to avoid the cast?

Yes, that should be fine. If we want, I can remove the helper and use iov_length() directly. I thought vringh wanted to hide iovec from users though.

Anyway talking to Jason, as a long term solution we should reconsider vringh and support iov_iter.

Thanks,
Stefano




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