Re: [PATCH] virtio: fix size computation according to the definition of struct vring_used in vring_size

[Wang Sheng-Hui <shhuiw@gmail.com>]

On 2011年08月27日 10:49, Wanlong Gao wrote:
> 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@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
> 

Thanks.

I checked the comments, and think we should patch vring_init
and vring_size according to the layout description in the comments.
Right?