netdev - Re: [BUG net-next] infamous dev refcnt leak... again.

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Date:	Fri, 14 Aug 2015 16:14:23 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>,
	David Ahern <dsa@...ulusnetworks.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: [BUG net-next] infamous dev refcnt leak... again.

On Fri, 2015-08-14 at 14:14 -0700, Eric Dumazet wrote:
> While rebooting host running latest net-next
> 
>  unregister_netdevice: waiting for eth0 to become free. Usage count = 4
> 
> Oh well...
> 

It looks like David Ahern recent changes uncover a bug ?

Not clear which commit is at fault.

Maybe 3bfd847203c6d89532f836ad3f5b4ff4ced26dd9 ?

Somehow a down device can be found.

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index b7f1d20..675a3b6 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -725,10 +725,14 @@ static int fib_check_nh(struct fib_config *cfg, struct fib_info *fi,
 		nh->nh_dev = dev = FIB_RES_DEV(res);
 		if (!dev)
 			goto out;
-		dev_hold(dev);
 		if (!netif_carrier_ok(dev))
 			nh->nh_flags |= RTNH_F_LINKDOWN;
-		err = (dev->flags & IFF_UP) ? 0 : -ENETDOWN;
+		if (dev->flags & IFF_UP) {
+			err = 0;
+			dev_hold(dev);
+		} else {
+			err = -ENETDOWN;
+		}
 	} else {
 		struct in_device *in_dev;
 


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