Messages in this thread | | | Date | Mon, 1 Feb 2021 11:23:20 +0100 | From | Stefano Garzarella <> | Subject | Re: [PATCH RFC v2 04/10] vringh: implement vringh_kiov_advance() |
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On Mon, Feb 01, 2021 at 01:43:23PM +0800, Jason Wang wrote: > >On 2021/1/28 下午10:41, Stefano Garzarella wrote: >>In some cases, it may be useful to provide a way to skip a number >>of bytes in a vringh_kiov. >> >>Let's implement vringh_kiov_advance() for this purpose, reusing the >>code from vringh_iov_xfer(). >>We replace that code calling the new vringh_kiov_advance(). > > >Acked-by: Jason Wang <jasowang@redhat.com> > >In the long run we need to switch to use iov iterator library instead.
Yes I agree. I've tried to do this, but it requires quite a bit of work to change vringh, I'll put it on my todo list.
Thanks, Stefano
> >Thanks > > >> >>Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> >>--- >> include/linux/vringh.h | 2 ++ >> drivers/vhost/vringh.c | 41 +++++++++++++++++++++++++++++------------ >> 2 files changed, 31 insertions(+), 12 deletions(-) >> >>diff --git a/include/linux/vringh.h b/include/linux/vringh.h >>index 9c077863c8f6..755211ebd195 100644 >>--- a/include/linux/vringh.h >>+++ b/include/linux/vringh.h >>@@ -199,6 +199,8 @@ static inline void vringh_kiov_cleanup(struct vringh_kiov *kiov) >> kiov->iov = NULL; >> } >>+void vringh_kiov_advance(struct vringh_kiov *kiov, size_t len); >>+ >> int vringh_getdesc_kern(struct vringh *vrh, >> struct vringh_kiov *riov, >> struct vringh_kiov *wiov, >>diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c >>index bee63d68201a..4d800e4f31ca 100644 >>--- a/drivers/vhost/vringh.c >>+++ b/drivers/vhost/vringh.c >>@@ -75,6 +75,34 @@ static inline int __vringh_get_head(const struct vringh *vrh, >> return head; >> } >>+/** >>+ * vringh_kiov_advance - skip bytes from vring_kiov >>+ * @iov: an iov passed to vringh_getdesc_*() (updated as we consume) >>+ * @len: the maximum length to advance >>+ */ >>+void vringh_kiov_advance(struct vringh_kiov *iov, size_t len) >>+{ >>+ while (len && iov->i < iov->used) { >>+ size_t partlen = min(iov->iov[iov->i].iov_len, len); >>+ >>+ iov->consumed += partlen; >>+ iov->iov[iov->i].iov_len -= partlen; >>+ iov->iov[iov->i].iov_base += partlen; >>+ >>+ if (!iov->iov[iov->i].iov_len) { >>+ /* Fix up old iov element then increment. */ >>+ iov->iov[iov->i].iov_len = iov->consumed; >>+ iov->iov[iov->i].iov_base -= iov->consumed; >>+ >>+ iov->consumed = 0; >>+ iov->i++; >>+ } >>+ >>+ len -= partlen; >>+ } >>+} >>+EXPORT_SYMBOL(vringh_kiov_advance); >>+ >> /* Copy some bytes to/from the iovec. Returns num copied. */ >> static inline ssize_t vringh_iov_xfer(struct vringh *vrh, >> struct vringh_kiov *iov, >>@@ -95,19 +123,8 @@ static inline ssize_t vringh_iov_xfer(struct vringh *vrh, >> done += partlen; >> len -= partlen; >> ptr += partlen; >>- iov->consumed += partlen; >>- iov->iov[iov->i].iov_len -= partlen; >>- iov->iov[iov->i].iov_base += partlen; >>- if (!iov->iov[iov->i].iov_len) { >>- /* Fix up old iov element then increment. */ >>- iov->iov[iov->i].iov_len = iov->consumed; >>- iov->iov[iov->i].iov_base -= iov->consumed; >>- >>- >>- iov->consumed = 0; >>- iov->i++; >>- } >>+ vringh_kiov_advance(iov, partlen); >> } >> return done; >> } >
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