virtio: modify vring_init and vring_size to take account of the layout containing *_event_idx

Based on the layout description in the comments, take account of
the *_event_idx in functions vring_init and vring_size.

Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 3 insertions, 3 deletions

diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
index 4a32cb6da425..36be0f6e18a9 100644
--- a/include/linux/virtio_ring.h
+++ b/include/linux/virtio_ring.h
@@ -135,13 +135,13 @@ static inline void vring_init(struct vring *vr, unsigned int num, void *p,
         vr->num = num;
         vr->desc = p;
         vr->avail = p + num*sizeof(struct vring_desc);
-        vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + align-1)
-                            & ~(align - 1));
+        vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + sizeof(__u16)
+                + align-1) & ~(align - 1));
 }
 
 static inline unsigned vring_size(unsigned int num, unsigned long align)
 {
-        return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
+        return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (3 + num)
                  + align - 1) & ~(align - 1))
                 + sizeof(__u16) * 3 + sizeof(struct vring_used_elem) * num;
 }