> Subject: Re: [EXTERNAL] Re: [Patch rdma-next] RDMA/mana_ib: handle net
> event for pointing to the current netdev
>
> On Tue, Mar 04, 2025 at 06:26:03PM +0000, Long Li wrote:
> > > On 2025-03-01 at 04:11:59, longli@xxxxxxxxxxxxxxxxx
> > > (longli@xxxxxxxxxxxxxxxxx) wrote:
> > > > From: Long Li <longli@xxxxxxxxxxxxx>
> > > >
> > > > When running under Hyper-V, the master device to the RDMA device
> > > > is always bonded to this RDMA device if it's present in the
> > > > kernel. This is not user-configurable.
> > > >
> > > > The master device can be unbind/bind from the kernel. During those
> > > > events, the RDMA device should set to the current netdev to relect
> > > > the change of master device from those events.
> > > >
> > > > Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
> > > > ---
> > > > drivers/infiniband/hw/mana/device.c | 35
> > > > ++++++++++++++++++++++++++++ drivers/infiniband/hw/mana/mana_ib.h
> > > > ++++++++++++++++++++++++++++ |
> > > > 1 +
> > > > 2 files changed, 36 insertions(+)
> > > >
> > > > diff --git a/drivers/infiniband/hw/mana/device.c
> > > > b/drivers/infiniband/hw/mana/device.c
> > > > index 3416a85f8738..3e4f069c2258 100644
> > > > --- a/drivers/infiniband/hw/mana/device.c
> > > > +++ b/drivers/infiniband/hw/mana/device.c
> > > > @@ -51,6 +51,37 @@ static const struct ib_device_ops mana_ib_dev_ops =
> {
> > > > ib_ind_table), };
> > > >
> > > > +static int mana_ib_netdev_event(struct notifier_block *this,
> > > > + unsigned long event, void *ptr) {
> > > > + struct mana_ib_dev *dev = container_of(this, struct mana_ib_dev, nb);
> > > > + struct net_device *event_dev = netdev_notifier_info_to_dev(ptr);
> > > > + struct gdma_context *gc = dev->gdma_dev->gdma_context;
> > > > + struct mana_context *mc = gc->mana.driver_data;
> > > > + struct net_device *ndev;
> > > > +
> > > > + if (event_dev != mc->ports[0])
> > > > + return NOTIFY_DONE;
> > > > +
> > > > + switch (event) {
> > > > + case NETDEV_CHANGEUPPER:
> > > > + rcu_read_lock();
> > > > + ndev = mana_get_primary_netdev_rcu(mc, 0);
> > > > + rcu_read_unlock();
> > > ...
> > > > +
> > > > + /*
> > > > + * 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);
> > > rcu_read_unlock() should be here, right ?
> >
> > It can't. ib_device_set_netdev() is calling alloc_port_data() and may sleep.
> >
> > I think this locking is okay. This event only comes in when:
> > 1. the master device has changed to netvsc. In this case ndev is guaranteed to
> be valid as this notification is triggered by netvsc.
> > 2. the master device has changed to itself (the ethernet device parent for the IB
> device). In this case, ndev is valid because mana_ib is an auxiliary device to ndev
> and it can't unload itself at this time.
>
>
> Why not return with the netdev refcount held so you don't need this weirdo rcu
> thing?
>
> Jason
I sent v3 with netdev refcount held. Thank you.
Long
