Re: [PATCH] vhost_net: clear msg.control for non-zerocopy case duringtx

[Sergei Shtylyov]

Hello.

On 06/06/2013 07:27 AM, 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:
> > > [<ffffffff81796b73>] dump_stack+0x19/0x1e
> > > [<ffffffff8103d66b>] warn_slowpath_common+0x6b/0xa0
> > > [<ffffffff8103d6b5>] warn_slowpath_null+0x15/0x20
> > > [<ffffffffa0197627>] handle_tx+0x477/0x4b0 [vhost_net]
> > > [<ffffffffa0197690>] handle_tx_kick+0x10/0x20 [vhost_net]
> > > [<ffffffffa019541e>] vhost_worker+0xfe/0x1a0 [vhost_net]
> > > [<ffffffffa0195320>] ? vhost_attach_cgroups_work+0x30/0x30 [vhost_net]
> > > [<ffffffffa0195320>] ? vhost_attach_cgroups_work+0x30/0x30 [vhost_net]
> > > [<ffffffff81061f46>] kthread+0xc6/0xd0
> > > [<ffffffff81061e80>] ? kthread_freezable_should_stop+0x70/0x70
> > > [<ffffffff817a1aec>] ret_from_fork+0x7c/0xb0
> > > [<ffffffff81061e80>] ? kthread_freezable_should_stop+0x70/0x70
> > > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> > > ---
> > >    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
> >     You have to use {} on the *else* branch if you have it of the *if*
> > branch (and vice versa), according to Documentation/CodingStyle.
> checkpatch.pl didn't complain this, will send v2.

    Yes, this check is what it seems to lack still.

> Thanks

WBR, Sergei

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