From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net 2/2] macvtap: handle ubuf refcount correctly when meet erros Date: Wed, 30 Nov 2016 15:58:05 +0200 Message-ID: <20161130155758-mutt-send-email-mst@kernel.org> References: <1480483072-14201-1-git-send-email-jasowang@redhat.com> <1480483072-14201-2-git-send-email-jasowang@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, wangyunjian@huawei.com To: Jason Wang Return-path: Received: from mx1.redhat.com ([209.132.183.28]:56266 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756914AbcK3N6J (ORCPT ); Wed, 30 Nov 2016 08:58:09 -0500 Content-Disposition: inline In-Reply-To: <1480483072-14201-2-git-send-email-jasowang@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Nov 30, 2016 at 01:17:52PM +0800, Jason Wang wrote: > We trigger uarg->callback() immediately after we decide do datacopy > even if caller want to do zerocopy. This will cause the callback > (vhost_net_zerocopy_callback) decrease the refcount. But when we meet > an error afterwards, the error handling in vhost handle_tx() will try > to decrease it again. This is wrong and fix this by delay the > uarg->callback() until we're sure there's no errors. > > Signed-off-by: Jason Wang Acked-by: Michael S. Tsirkin > --- > The patch is needed for -stable. > --- > drivers/net/macvtap.c | 11 +++++------ > 1 file changed, 5 insertions(+), 6 deletions(-) > > diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c > index bceca28..7869b06 100644 > --- a/drivers/net/macvtap.c > +++ b/drivers/net/macvtap.c > @@ -742,13 +742,8 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m, > > if (zerocopy) > err = zerocopy_sg_from_iter(skb, from); > - else { > + else > err = skb_copy_datagram_from_iter(skb, 0, from, len); > - if (!err && m && m->msg_control) { > - struct ubuf_info *uarg = m->msg_control; > - uarg->callback(uarg, false); > - } > - } > > if (err) > goto err_kfree; > @@ -779,7 +774,11 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m, > skb_shinfo(skb)->destructor_arg = m->msg_control; > skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY; > skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG; > + } else if (m && m->msg_control) { > + struct ubuf_info *uarg = m->msg_control; > + uarg->callback(uarg, false); > } > + > if (vlan) { > skb->dev = vlan->dev; > dev_queue_xmit(skb); > -- > 2.7.4