netdev - [PATCH net-next 05/10] decnet: use __dev_get_by_index instead of dev_get_by

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Date:	Tue, 14 Jan 2014 15:41:04 +0800
From:	Ying Xue <ying.xue@...driver.com>
To:	<davem@...emloft.net>
CC:	<vfalico@...hat.com>, <john.r.fastabend@...el.com>,
	<stephen@...workplumber.org>, <antonio@...hcoding.com>,
	<dmitry.tarnyagin@...kless.no>, <socketcan@...tkopp.net>,
	<johannes@...solutions.net>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH net-next 05/10] decnet: use __dev_get_by_index instead of dev_get_by_index to find interface

The following call chain we can identify that dn_cache_getroute() is
protected under rtnl_lock. So if we use __dev_get_by_index() instead
of dev_get_by_index() to find interface handlers in it, this would help
us avoid to change interface reference counter.

rtnetlink_rcv()
  rtnl_lock()
    netlink_rcv_skb()
      dn_cache_getroute()
  rtnl_unlock()

Signed-off-by: Ying Xue <ying.xue@...driver.com>
---
 net/decnet/dn_route.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index ad2efa5..22390e4 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -1666,12 +1666,12 @@ static int dn_cache_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh)
 
 	if (fld.flowidn_iif) {
 		struct net_device *dev;
-		if ((dev = dev_get_by_index(&init_net, fld.flowidn_iif)) == NULL) {
+		dev = __dev_get_by_index(&init_net, fld.flowidn_iif);
+		if (!dev) {
 			kfree_skb(skb);
 			return -ENODEV;
 		}
 		if (!dev->dn_ptr) {
-			dev_put(dev);
 			kfree_skb(skb);
 			return -ENODEV;
 		}
@@ -1693,8 +1693,6 @@ static int dn_cache_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh)
 		err = dn_route_output_key((struct dst_entry **)&rt, &fld, 0);
 	}
 
-	if (skb->dev)
-		dev_put(skb->dev);
 	skb->dev = NULL;
 	if (err)
 		goto out_free;
-- 
1.7.9.5

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