From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH] vhost_net: clear msg.control for non-zerocopy case during tx Date: Wed, 5 Jun 2013 12:02:52 +0300 Message-ID: <20130605090252.GA31830@redhat.com> References: <1370418046-11851-1-git-send-email-jasowang@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org To: Jason Wang Return-path: Content-Disposition: inline In-Reply-To: <1370418046-11851-1-git-send-email-jasowang@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: netdev.vger.kernel.org On Wed, Jun 05, 2013 at 03:40:46PM +0800, Jason Wang wrote: > When we decide not use zero-copy, msg.control should be set to NULL otherwise > macvtap/tap may set zerocopy callbacks which may decrease the kref of ubufs > wrongly. > > Bug were introduced by commit cedb9bdce099206290a2bdd02ce47a7b253b6a84 > (vhost-net: skip head management if no outstanding). > > This solves the following warnings: > > WARNING: at include/linux/kref.h:47 handle_tx+0x477/0x4b0 [vhost_net]() > Modules linked in: vhost_net macvtap macvlan tun nfsd exportfs bridge stp llc openvswitch kvm_amd kvm bnx2 megaraid_sas [last unloaded: tun] > CPU: 5 PID: 8670 Comm: vhost-8668 Not tainted 3.10.0-rc2+ #1566 > Hardware name: Dell Inc. PowerEdge R715/00XHKG, BIOS 1.5.2 04/19/2011 > ffffffffa0198323 ffff88007c9ebd08 ffffffff81796b73 ffff88007c9ebd48 > ffffffff8103d66b 000000007b773e20 ffff8800779f0000 ffff8800779f43f0 > ffff8800779f8418 000000000000015c 0000000000000062 ffff88007c9ebd58 > Call Trace: > [] dump_stack+0x19/0x1e > [] warn_slowpath_common+0x6b/0xa0 > [] warn_slowpath_null+0x15/0x20 > [] handle_tx+0x477/0x4b0 [vhost_net] > [] handle_tx_kick+0x10/0x20 [vhost_net] > [] vhost_worker+0xfe/0x1a0 [vhost_net] > [] ? vhost_attach_cgroups_work+0x30/0x30 [vhost_net] > [] ? vhost_attach_cgroups_work+0x30/0x30 [vhost_net] > [] kthread+0xc6/0xd0 > [] ? kthread_freezable_should_stop+0x70/0x70 > [] ret_from_fork+0x7c/0xb0 > [] ? kthread_freezable_should_stop+0x70/0x70 > > Signed-off-by: Jason Wang Good catch. Acked-by: Michael S. Tsirkin This needs to go into stable as well. > --- > drivers/vhost/net.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > index 2b51e23..b07d96b 100644 > --- a/drivers/vhost/net.c > +++ b/drivers/vhost/net.c > @@ -436,7 +436,8 @@ static void handle_tx(struct vhost_net *net) > kref_get(&ubufs->kref); > } > nvq->upend_idx = (nvq->upend_idx + 1) % UIO_MAXIOV; > - } > + } else > + msg.msg_control = NULL; > /* TODO: Check specific error and bomb out unless ENOBUFS? */ > err = sock->ops->sendmsg(NULL, sock, &msg, len); > if (unlikely(err < 0)) { > -- > 1.7.1