[1/2] macvtap: remove useless codes in macvtap_aio_read() and macvtap_recvmsg()

From: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>

By checking related codes, it is impossible that ret > len or total_len,
so we should remove some useless coeds in both above functions.

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 drivers/net/macvtap.c |    5 -----
 1 files changed, 0 insertions(+), 5 deletions(-)

On 12/06/2013 03:54 PM, Zhi Yong Wu wrote:
> From: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
> 
> By checking related codes, it is impossible that ret > len or total_len,
> so we should remove some useless coeds in both above functions.

Looks like commit 6680ec68eff47d36f67b4351bc9836fd6cba9532
Author: Jason Wang <jasowang@redhat.com>
Date:   Thu Jul 25 13:00:33 2013 +0800

    tuntap: hardware vlan tx support

Introduced a change in tun_put_user() where we can
never return a length longer then len or total_len.
This has an effect that is now impossible to signal
truncated status.  It seems like a potential loss
of functionality and it might make sense to restore it.

-vlad
> 
> Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
> ---
>  drivers/net/macvtap.c |    5 -----
>  1 files changed, 0 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
> index 4c6f84c..7f4ccdd 100644
> --- a/drivers/net/macvtap.c
> +++ b/drivers/net/macvtap.c
> @@ -871,7 +871,6 @@ static ssize_t macvtap_aio_read(struct kiocb *iocb, const struct iovec *iv,
>  	}
>  
>  	ret = macvtap_do_read(q, iv, len, file->f_flags & O_NONBLOCK);
> -	ret = min_t(ssize_t, ret, len); /* XXX copied from tun.c. Why? */
>  out:
>  	return ret;
>  }
> @@ -1104,10 +1103,6 @@ static int macvtap_recvmsg(struct kiocb *iocb, struct socket *sock,
>  		return -EINVAL;
>  	ret = macvtap_do_read(q, m->msg_iov, total_len,
>  			  flags & MSG_DONTWAIT);
> -	if (ret > total_len) {
> -		m->msg_flags |= MSG_TRUNC;
> -		ret = flags & MSG_TRUNC ? ret : total_len;
> -	}
>  	return ret;
>  }
>  
> 

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On 12/07/2013 10:38 AM, Vlad Yasevich wrote:
> On 12/06/2013 03:54 PM, Zhi Yong Wu wrote:
>> > From: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
>> > 
>> > By checking related codes, it is impossible that ret > len or total_len,
>> > so we should remove some useless coeds in both above functions.
> Looks like commit 6680ec68eff47d36f67b4351bc9836fd6cba9532
> Author: Jason Wang <jasowang@redhat.com>
> Date:   Thu Jul 25 13:00:33 2013 +0800
>
>     tuntap: hardware vlan tx support
>
> Introduced a change in tun_put_user() where we can
> never return a length longer then len or total_len.
> This has an effect that is now impossible to signal
> truncated status.  It seems like a potential loss
> of functionality and it might make sense to restore it.
>
> -vlad

True, will send a patch. For macvtap, we'd better also correct current
behaviour to be same with tun.

Thanks
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From: Zhi Yong Wu <zwu.kernel@gmail.com>
Date: Sat,  7 Dec 2013 04:54:59 +0800

> From: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
> 
> By checking related codes, it is impossible that ret > len or total_len,
> so we should remove some useless coeds in both above functions.
> 
> Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>

Applied.
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