[net PATCH] tuntap: set SOCK_ZEROCOPY flag during open

[net PATCH] tuntap: set SOCK_ZEROCOPY flag during open

[Jason Wang]

Commit 54f968d6efdbf7dec36faa44fc11f01b0e4d1990
(tuntap: move socket to tun_file) forgets to set SOCK_ZEROCOPY flag, which will
prevent vhost_net from doing zercopy w/ tap. This patch fixes this by setting
it during file open.

Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/net/tun.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index f042b03..d2ddd6d 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2155,6 +2155,8 @@ static int tun_chr_open(struct inode *inode, struct file * file)
 	set_bit(SOCK_EXTERNALLY_ALLOCATED, &tfile->socket.flags);
 	INIT_LIST_HEAD(&tfile->next);
 
+	sock_set_flag(&tfile->sk, SOCK_ZEROCOPY);
+
 	return 0;
 }
 
-- 
1.7.1

Re: [net PATCH] tuntap: set SOCK_ZEROCOPY flag during open

[Michael S. Tsirkin]

On Sat, Jun 08, 2013 at 02:17:41PM +0800, Jason Wang wrote:
> Commit 54f968d6efdbf7dec36faa44fc11f01b0e4d1990
> (tuntap: move socket to tun_file) forgets to set SOCK_ZEROCOPY flag, which will
> prevent vhost_net from doing zercopy w/ tap. This patch fixes this by setting
> it during file open.
> 
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>

I see, and this explains the perf regression we are seeing with 3.9.

Acked-by: Michael S. Tsirkin <mst@redhat.com>

and I think this should go into stable as well.

> ---
>  drivers/net/tun.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index f042b03..d2ddd6d 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -2155,6 +2155,8 @@ static int tun_chr_open(struct inode *inode, struct file * file)
>  	set_bit(SOCK_EXTERNALLY_ALLOCATED, &tfile->socket.flags);
>  	INIT_LIST_HEAD(&tfile->next);
>  
> +	sock_set_flag(&tfile->sk, SOCK_ZEROCOPY);
> +
>  	return 0;
>  }
>  
> -- 
> 1.7.1

Re: [net PATCH] tuntap: set SOCK_ZEROCOPY flag during open

[Michael S. Tsirkin]

On Sat, Jun 08, 2013 at 02:17:41PM +0800, Jason Wang wrote:
>Cc: smtp.corp.redhat.com@redhat.com, davem@davemloft.net,
>	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
>
> Commit 54f968d6efdbf7dec36faa44fc11f01b0e4d1990
> (tuntap: move socket to tun_file) forgets to set SOCK_ZEROCOPY flag, which will
> prevent vhost_net from doing zercopy w/ tap. This patch fixes this by setting
> it during file open.
> 
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>

One of the addresses in the Cc list (smtp.corp.redhat.com@redhat.com)
is clearly a mistake, which probably explains why it didn't
get into patchwork.

I have bounced it to correct addresses, hope this
helps instead of making even more of a mess of it.

For 3.10 and -stable:

Acked-by: Michael S. Tsirkin <mst@redhat.com>


> ---
>  drivers/net/tun.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index f042b03..d2ddd6d 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -2155,6 +2155,8 @@ static int tun_chr_open(struct inode *inode, struct file * file)
>  	set_bit(SOCK_EXTERNALLY_ALLOCATED, &tfile->socket.flags);
>  	INIT_LIST_HEAD(&tfile->next);
>  
> +	sock_set_flag(&tfile->sk, SOCK_ZEROCOPY);
> +
>  	return 0;
>  }
>  
> -- 
> 1.7.1

Re: [net PATCH] tuntap: set SOCK_ZEROCOPY flag during open

[David Miller]

From: "Michael S. Tsirkin" <mst@redhat.com>
Date: Tue, 11 Jun 2013 16:17:50 +0300

> On Sat, Jun 08, 2013 at 02:17:41PM +0800, Jason Wang wrote:
>>Cc: smtp.corp.redhat.com@redhat.com, davem@davemloft.net,
>>	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
>>
>> Commit 54f968d6efdbf7dec36faa44fc11f01b0e4d1990
>> (tuntap: move socket to tun_file) forgets to set SOCK_ZEROCOPY flag, which will
>> prevent vhost_net from doing zercopy w/ tap. This patch fixes this by setting
>> it during file open.
>> 
>> Cc: Michael S. Tsirkin <mst@redhat.com>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
> 
> One of the addresses in the Cc list (smtp.corp.redhat.com@redhat.com)
> is clearly a mistake, which probably explains why it didn't
> get into patchwork.
> 
> I have bounced it to correct addresses, hope this
> helps instead of making even more of a mess of it.
> 
> For 3.10 and -stable:
> 
> Acked-by: Michael S. Tsirkin <mst@redhat.com>

Applied and queued up for -stable, thanks.