Linux Virtualization - Aug 2011 - [PATCH] virtio: fix size computation according to the definition of struct vring_used in vring_size

The patch is against 3.1-rc3.

struct vring_used has two __u16 fields plus array of struct vring_used_elem.
Current vring_size counts the __u16 fields to 3. Fix it to 2 in the patch.

Signed-off-by: Wang Sheng-Hui <shhuiw at gmail.com>
---
 include/linux/virtio_ring.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
index 4a32cb6..fcda152 100644
--- a/include/linux/virtio_ring.h
+++ b/include/linux/virtio_ring.h
@@ -143,7 +143,7 @@ static inline unsigned vring_size(unsigned int num, unsigned
long align)
 {
 	return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
 		 + align - 1) & ~(align - 1))
-		+ sizeof(__u16) * 3 + sizeof(struct vring_used_elem) * num;
+		+ sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num;
 }
 
 /* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */
-- 
1.7.1

crossover at crossover-plinux:~/dev/patchwork$

On Sat, 2011-08-27 at 09:07 +0800, Wang Sheng-Hui wrote:
> The patch is against 3.1-rc3.
> 
> struct vring_used has two __u16 fields plus array of struct
vring_used_elem.
> Current vring_size counts the __u16 fields to 3. Fix it to 2 in the patch.
> 
> Signed-off-by: Wang Sheng-Hui <shhuiw at gmail.com>
> ---
>  include/linux/virtio_ring.h |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
> index 4a32cb6..fcda152 100644
> --- a/include/linux/virtio_ring.h
> +++ b/include/linux/virtio_ring.h
> @@ -143,7 +143,7 @@ static inline unsigned vring_size(unsigned int num,
unsigned long align)
>  {
>  	return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
>  		 + align - 1) & ~(align - 1))
> -		+ sizeof(__u16) * 3 + sizeof(struct vring_used_elem) * num;
> +		+ sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num;
>  }
>  
>  /* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */
Hi:
I'm not deep into it, but I think you can see this:
http://marc.info/?l=git-commits-head&m=130687915816130&w=2

Thanks
-Wanlong Gao