Commit b8c06ad4 authored by Stefano Garzarella's avatar Stefano Garzarella Committed by Michael S. Tsirkin
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vringh: implement vringh_kiov_advance() 



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: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarStefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/r/20210315163450.254396-6-sgarzare@redhat.com


Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 69c13c58

drivers/vhost/vringh.c

+29 −12
Original line number Diff line number Diff line
@@ -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;

}

include/linux/vringh.h

+2 −0
Original line number Diff line number Diff line
@@ -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,