[RFC PATCH 2/9] vringh: remove vringh_iov and unite to vringh_kiov

[Shunsuke Mie]

struct vringh_iov is defined to hold userland addresses. However, to use
common function, __vring_iov, finally the vringh_iov converts to the
vringh_kiov with simple cast. It includes compile time check code to make
sure it can be cast correctly.

To simplify the code, this patch removes the struct vringh_iov and unifies
APIs to struct vringh_kiov.

Signed-off-by: Shunsuke Mie <mie@xxxxxxxxxx>
---
 drivers/vhost/vringh.c | 32 ++++++------------------------
 include/linux/vringh.h | 45 ++++--------------------------------------
 2 files changed, 10 insertions(+), 67 deletions(-)

diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index 828c29306565..aa3cd27d2384 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -691,8 +691,8 @@ EXPORT_SYMBOL(vringh_init_user);
  * calling vringh_iov_cleanup() to release the memory, even on error!
  */
 int vringh_getdesc_user(struct vringh *vrh,
-			struct vringh_iov *riov,
-			struct vringh_iov *wiov,
+			struct vringh_kiov *riov,
+			struct vringh_kiov *wiov,
 			bool (*getrange)(struct vringh *vrh,
 					 u64 addr, struct vringh_range *r),
 			u16 *head)
@@ -708,26 +708,6 @@ int vringh_getdesc_user(struct vringh *vrh,
 	if (err == vrh->vring.num)
 		return 0;
 
-	/* We need the layouts to be the identical for this to work */
-	BUILD_BUG_ON(sizeof(struct vringh_kiov) != sizeof(struct vringh_iov));
-	BUILD_BUG_ON(offsetof(struct vringh_kiov, iov) !=
-		     offsetof(struct vringh_iov, iov));
-	BUILD_BUG_ON(offsetof(struct vringh_kiov, i) !=
-		     offsetof(struct vringh_iov, i));
-	BUILD_BUG_ON(offsetof(struct vringh_kiov, used) !=
-		     offsetof(struct vringh_iov, used));
-	BUILD_BUG_ON(offsetof(struct vringh_kiov, max_num) !=
-		     offsetof(struct vringh_iov, max_num));
-	BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
-	BUILD_BUG_ON(offsetof(struct iovec, iov_base) !=
-		     offsetof(struct kvec, iov_base));
-	BUILD_BUG_ON(offsetof(struct iovec, iov_len) !=
-		     offsetof(struct kvec, iov_len));
-	BUILD_BUG_ON(sizeof(((struct iovec *)NULL)->iov_base)
-		     != sizeof(((struct kvec *)NULL)->iov_base));
-	BUILD_BUG_ON(sizeof(((struct iovec *)NULL)->iov_len)
-		     != sizeof(((struct kvec *)NULL)->iov_len));
-
 	*head = err;
 	err = __vringh_iov(vrh, *head, (struct vringh_kiov *)riov,
 			   (struct vringh_kiov *)wiov,
@@ -740,14 +720,14 @@ int vringh_getdesc_user(struct vringh *vrh,
 EXPORT_SYMBOL(vringh_getdesc_user);
 
 /**
- * vringh_iov_pull_user - copy bytes from vring_iov.
+ * vringh_iov_pull_user - copy bytes from vring_kiov.
  * @riov: the riov as passed to vringh_getdesc_user() (updated as we consume)
  * @dst: the place to copy.
  * @len: the maximum length to copy.
  *
  * Returns the bytes copied <= len or a negative errno.
  */
-ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len)
+ssize_t vringh_iov_pull_user(struct vringh_kiov *riov, void *dst, size_t len)
 {
 	return vringh_iov_xfer(NULL, (struct vringh_kiov *)riov,
 			       dst, len, xfer_from_user);
@@ -755,14 +735,14 @@ ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len)
 EXPORT_SYMBOL(vringh_iov_pull_user);
 
 /**
- * vringh_iov_push_user - copy bytes into vring_iov.
+ * vringh_iov_push_user - copy bytes into vring_kiov.
  * @wiov: the wiov as passed to vringh_getdesc_user() (updated as we consume)
  * @src: the place to copy from.
  * @len: the maximum length to copy.
  *
  * Returns the bytes copied <= len or a negative errno.
  */
-ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
+ssize_t vringh_iov_push_user(struct vringh_kiov *wiov,
 			     const void *src, size_t len)
 {
 	return vringh_iov_xfer(NULL, (struct vringh_kiov *)wiov,
diff --git a/include/linux/vringh.h b/include/linux/vringh.h
index 1991a02c6431..733d948e8123 100644
--- a/include/linux/vringh.h
+++ b/include/linux/vringh.h
@@ -79,18 +79,6 @@ struct vringh_range {
 	u64 offset;
 };
 
-/**
- * struct vringh_iov - iovec mangler.
- *
- * Mangles iovec in place, and restores it.
- * Remaining data is iov + i, of used - i elements.
- */
-struct vringh_iov {
-	struct iovec *iov;
-	size_t consumed; /* Within iov[i] */
-	unsigned i, used, max_num;
-};
-
 /**
  * struct vringh_kiov - kvec mangler.
  *
@@ -113,44 +101,19 @@ int vringh_init_user(struct vringh *vrh, u64 features,
 		     vring_avail_t __user *avail,
 		     vring_used_t __user *used);
 
-static inline void vringh_iov_init(struct vringh_iov *iov,
-				   struct iovec *iovec, unsigned num)
-{
-	iov->used = iov->i = 0;
-	iov->consumed = 0;
-	iov->max_num = num;
-	iov->iov = iovec;
-}
-
-static inline void vringh_iov_reset(struct vringh_iov *iov)
-{
-	iov->iov[iov->i].iov_len += iov->consumed;
-	iov->iov[iov->i].iov_base -= iov->consumed;
-	iov->consumed = 0;
-	iov->i = 0;
-}
-
-static inline void vringh_iov_cleanup(struct vringh_iov *iov)
-{
-	if (iov->max_num & VRINGH_IOV_ALLOCATED)
-		kfree(iov->iov);
-	iov->max_num = iov->used = iov->i = iov->consumed = 0;
-	iov->iov = NULL;
-}
-
 /* Convert a descriptor into iovecs. */
 int vringh_getdesc_user(struct vringh *vrh,
-			struct vringh_iov *riov,
-			struct vringh_iov *wiov,
+			struct vringh_kiov *riov,
+			struct vringh_kiov *wiov,
 			bool (*getrange)(struct vringh *vrh,
 					 u64 addr, struct vringh_range *r),
 			u16 *head);
 
 /* Copy bytes from readable vsg, consuming it (and incrementing wiov->i). */
-ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len);
+ssize_t vringh_iov_pull_user(struct vringh_kiov *riov, void *dst, size_t len);
 
 /* Copy bytes into writable vsg, consuming it (and incrementing wiov->i). */
-ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
+ssize_t vringh_iov_push_user(struct vringh_kiov *wiov,
 			     const void *src, size_t len);
 
 /* Mark a descriptor as used. */
-- 
2.25.1