linux-kernel - RE: [EXTERNAL] Re: [patch rdma-next v5 2/2] RDMA/mana_ib: Handle net event for pointing to the current netdev

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Message-ID:
 <SA6PR21MB4231E9B17697BFE4857A7E55CECA2@SA6PR21MB4231.namprd21.prod.outlook.com>
Date: Thu, 6 Mar 2025 20:01:45 +0000
From: Long Li <longli@...rosoft.com>
To: Jason Gunthorpe <jgg@...pe.ca>, "longli@...uxonhyperv.com"
	<longli@...uxonhyperv.com>
CC: Leon Romanovsky <leon@...nel.org>, Konstantin Taranov
	<kotaranov@...rosoft.com>, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, "linux-rdma@...r.kernel.org"
	<linux-rdma@...r.kernel.org>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-hyperv@...r.kernel.org"
	<linux-hyperv@...r.kernel.org>
Subject: RE: [EXTERNAL] Re: [patch rdma-next v5 2/2] RDMA/mana_ib: Handle net
 event for pointing to the current netdev

> Subject: [EXTERNAL] Re: [patch rdma-next v5 2/2] RDMA/mana_ib: Handle net
> event for pointing to the current netdev
> 
> On Thu, Mar 06, 2025 at 11:24:39AM -0800, longli@...uxonhyperv.com wrote:
> > +	switch (event) {
> > +	case NETDEV_CHANGEUPPER:
> > +		ndev = mana_get_primary_netdev(mc, 0, &dev->dev_tracker);
> > +		/*
> > +		 * RDMA core will setup GID based on updated netdev.
> > +		 * It's not possible to race with the core as rtnl lock is being
> > +		 * held.
> > +		 */
> > +		ib_device_set_netdev(&dev->ib_dev, ndev, 1);
> > +
> > +		/* mana_get_primary_netdev() returns ndev with refcount held
> */
> > +		netdev_put(ndev, &dev->dev_tracker);
> 
> ? What is the point of a tracker in dev if it never lasts outside this scope?
> 
> ib_device_set_netdev() already has a tracker built into it.
> 
> Jason

I was asked to use a tracker for netdev_hold()/netdev_put(). But this code (and the code in mana_ib_probe() of the 1st patch) is simple enough that everything is done in one scope.

Jakub, do you think it's okay to use NULL as the tracker in both patches?

Long