dcb: use __dev_get_by_name instead of dev_get_by_name to find interface

The following call chain indicates that dcb_doit() is protected
under rtnl_lock. So if we use __dev_get_by_name() instead of
dev_get_by_name() to find interface handlers in it, this would
help us avoid to change interface reference counter.

rtnetlink_rcv()
  rtnl_lock()
  netlink_rcv_skb()
    dcb_doit()
  rtnl_unlock()

Cc: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/dcb/dcbnl.c b/net/dcb/dcbnl.c
index 66fbe19..5536444 100644 (file)
--- a/net/dcb/dcbnl.c
+++ b/net/dcb/dcbnl.c
@@ -1688,21 +1688,17 @@ static int dcb_doit(struct sk_buff *skb, struct nlmsghdr *nlh)
        if (!tb[DCB_ATTR_IFNAME])
                return -EINVAL;
 
-       netdev = dev_get_by_name(net, nla_data(tb[DCB_ATTR_IFNAME]));
+       netdev = __dev_get_by_name(net, nla_data(tb[DCB_ATTR_IFNAME]));
        if (!netdev)
                return -ENODEV;
 
-       if (!netdev->dcbnl_ops) {
-               ret = -EOPNOTSUPP;
-               goto out;
-       }
+       if (!netdev->dcbnl_ops)
+               return -EOPNOTSUPP;
 
        reply_skb = dcbnl_newmsg(fn->type, dcb->cmd, portid, nlh->nlmsg_seq,
                                 nlh->nlmsg_flags, &reply_nlh);
-       if (!reply_skb) {
-               ret = -ENOBUFS;
-               goto out;
-       }
+       if (!reply_skb)
+               return -ENOBUFS;
 
        ret = fn->cb(netdev, nlh, nlh->nlmsg_seq, tb, reply_skb);
        if (ret < 0) {
@@ -1714,7 +1710,6 @@ static int dcb_doit(struct sk_buff *skb, struct nlmsghdr *nlh)
 
        ret = rtnl_unicast(reply_skb, net, portid);
 out:
-       dev_put(netdev);
        return ret;
 }