netdev - Re: [PATCH rdma-next 1/2] RDMA/mlx5: Get upper device only if device is lagged

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Date: Sun, 20 Aug 2023 12:59:26 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: Mark Bloch <mbloch@...dia.com>, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, linux-rdma@...r.kernel.org,
	Mark Zhang <markzhang@...dia.com>, netdev@...r.kernel.org,
	Paolo Abeni <pabeni@...hat.com>, Saeed Mahameed <saeedm@...dia.com>
Subject: Re: [PATCH rdma-next 1/2] RDMA/mlx5: Get upper device only if device
 is lagged

On Fri, Aug 18, 2023 at 01:42:30PM -0300, Jason Gunthorpe wrote:
> On Fri, Aug 18, 2023 at 01:33:35PM -0300, Jason Gunthorpe wrote:
> > On Wed, Aug 16, 2023 at 09:52:23AM +0300, Leon Romanovsky wrote:
> > > From: Mark Bloch <mbloch@...dia.com>
> > > 
> > > If the RDMA device isn't in LAG mode there is no need
> > > to try to get the upper device.
> > > 
> > > Signed-off-by: Mark Bloch <mbloch@...dia.com>
> > > Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> > > ---
> > >  drivers/infiniband/hw/mlx5/main.c | 22 +++++++++++++++-------
> > >  1 file changed, 15 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c
> > > index f0b394ed7452..215d7b0add8f 100644
> > > --- a/drivers/infiniband/hw/mlx5/main.c
> > > +++ b/drivers/infiniband/hw/mlx5/main.c
> > > @@ -195,12 +195,18 @@ static int mlx5_netdev_event(struct notifier_block *this,
> > >  	case NETDEV_CHANGE:
> > >  	case NETDEV_UP:
> > >  	case NETDEV_DOWN: {
> > > -		struct net_device *lag_ndev = mlx5_lag_get_roce_netdev(mdev);
> > >  		struct net_device *upper = NULL;
> > >  
> > > -		if (lag_ndev) {
> > > -			upper = netdev_master_upper_dev_get(lag_ndev);
> > > -			dev_put(lag_ndev);
> > > +		if (ibdev->lag_active) {
> > 
> > Needs locking to read lag_active
> 
> Specifically the use of the bitfield looks messed up.. If lag_active
> and some others were set only during probe it could be OK.

All fields except ib_active are static and set during probe.

> 
> But mixing other stuff that is being written concurrently is not OK to
> do like this. (eg ib_active via a mlx5 notifier)

What you are looking is the following change, did I get you right?

diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h
index 9d0c56b59ed2..ee73113717b2 100644
--- a/drivers/infiniband/hw/mlx5/mlx5_ib.h
+++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h
@@ -1094,7 +1094,7 @@ struct mlx5_ib_dev {
        /* serialize update of capability mask
         */
        struct mutex                    cap_mask_mutex;
-       u8                              ib_active:1;
+       bool                            ib_active;
        u8                              is_rep:1;
        u8                              lag_active:1;
        u8                              wc_support:1;

> 
> Jason