netdev - Re: xfrm, ip tunnel: non released device reference upon device unregistration

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Message-ID: <20180211154648.GA24719@breakpoint.cc>
Date:   Sun, 11 Feb 2018 16:46:48 +0100
From:   Florian Westphal <fw@...len.de>
To:     Eyal Birger <eyal.birger@...il.com>
Cc:     Florian Westphal <fw@...len.de>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        netdev@...r.kernel.org, herbert@...dor.apana.org.au,
        davem@...emloft.net, shmulik@...anetworks.com
Subject: Re: xfrm, ip tunnel: non released device reference upon device
 unregistration

Eyal Birger <eyal.birger@...il.com> wrote:

Sorry for taking so long to respond.

> On Tue, 6 Feb 2018 14:15:09 +0100
> Florian Westphal <fw@...len.de> wrote:
> 
> > Steffen Klassert <steffen.klassert@...unet.com> wrote:
> > > I gave the patch a quick try, but still I get this:
> > > 
> > > unregister_netdevice: waiting for dummy1 to become free. Usage
> > > count = 2  
> > 
> > Was that with Eyals setup or the bridge one I posted?
> > 
> > If it was Eyals setup, its possible the patch missed hookup
> > to whatever tunnel infra is used (the setup I used has ipip tunnel,
> > everything is ipv4).
> > 
> 
> Thanks!
> 
> Indeed the setup I'm testing uses ip6_tunnel.
> I have tested a fix in the spirit of the patch and it looks valid 
> for ip6_tunnel as well.
>
> It looks though that this change would need to be added to any tunnel
> device using dst_cache (vxlan, geneve, gre, ...).

Yes.  Meanwhile I tested your patch and it works for me too.
As your patch is shorter and ipv4/ipv6 seem to take care of refcount
put just fine I think your patch is the right way to go.

The xfrm_dst size incrase isn't much of a big deal, there is ample of
padding at the end so it will still be allocated from same slab.

We could reduce num_pols and num_xfrms to u8, which creates a 16 bit
hole, then store the cpu number instead of a list pointer.

This would limit growth to 16 instead of 24.

But, as I said, i do not think its a big deal.

> I'm wondering - non-xfrm dsts are already correctly invalidated,
> so do you think it makes sense to invalidate caches for devices that
> have no xfrm dsts? or maybe I didn't understand the suggestion?

See above, I think your patch is the way to go.