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Date: Mon, 26 Feb 2024 07:05:18 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: David Wei <dw@davidwei.uk>
Cc: Jiri Pirko <jiri@resnulli.us>, Sabrina Dubroca <sd@queasysnail.net>,
 maciek@machnikowski.net, horms@kernel.org, netdev@vger.kernel.org, "David
 S. Miller" <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>, Paolo
 Abeni <pabeni@redhat.com>
Subject: Re: [PATCH net-next v13 1/4] netdevsim: allow two netdevsim ports
 to be connected
Message-ID: <20240226070518.74898fe7@kernel.org>
In-Reply-To: <c51765ec-b072-4c01-8dce-c2fa51f1941c@davidwei.uk>
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On Sat, 24 Feb 2024 09:33:02 -0800 David Wei wrote:
> >> +	err = 0;  
> > 
> > Why zero..   
> 
> Sorry left over from a previous iteration.
> 
> >   
> >> +	nsim_a = netdev_priv(dev_a);
> >> +	peer = rtnl_dereference(nsim_a->peer);
> >> +	if (peer) {
> >> +		pr_err("Netdevsim %d:%u is already linked\n", netnsfd_a, ifidx_a);
> >> +		goto out_err;  
> > 
> > I'd think if we hit this we should return -EBUSY?
> > Unless peer == dev_b, but that may be splitting hair.  
> 
> What would returning -EBUSY do?

This is continuation of the previous comment, you set err to zero,
so when device already has a peer user will get 0 (success)
They should get -EBUSY.