> -----Original Message-----
> From: Jason Gunthorpe <jgg@xxxxxxxx>
> Sent: Tuesday, December 10, 2024 3:56 PM
> To: Bernard Metzler <BMT@xxxxxxxxxxxxxx>
> Cc: linux-rdma@xxxxxxxxxxxxxxx; leon@xxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; syzkaller-
> bugs@xxxxxxxxxxxxxxxx; zyjzyj2000@xxxxxxxxx;
> syzbot+4b87489410b4efd181bf@xxxxxxxxxxxxxxxxxxxxxxxxx
> Subject: [EXTERNAL] Re: [PATCH] RDMA/siw: Remove direct link to net_device
>
> On Tue, Dec 10, 2024 at 02:03:51PM +0100, Bernard Metzler wrote:
> > diff --git a/drivers/infiniband/sw/siw/siw.h
> b/drivers/infiniband/sw/siw/siw.h
> > index 86d4d6a2170e..c8f75527b513 100644
> > --- a/drivers/infiniband/sw/siw/siw.h
> > +++ b/drivers/infiniband/sw/siw/siw.h
> > @@ -69,16 +69,19 @@ struct siw_pd {
> >
> > struct siw_device {
> > struct ib_device base_dev;
> > - struct net_device *netdev;
> > struct siw_dev_cap attrs;
> >
> > u32 vendor_part_id;
> > + struct {
> > + int ifindex;
>
> ifindex is only stable so long as you are holding a reference on the
> netdev..
> > --- a/drivers/infiniband/sw/siw/siw_main.c
> > +++ b/drivers/infiniband/sw/siw/siw_main.c
> > @@ -287,7 +287,6 @@ static struct siw_device *siw_device_create(struct
> net_device *netdev)
> > return NULL;
> >
> > base_dev = &sdev->base_dev;
> > - sdev->netdev = netdev;
>
> Like here needed to grab a reference before storing the pointer in the
> sdev struct.
>
This patch was supposed to remove siw's link to netdev. So no
reference to netdev would be needed. I did it under the
assumption siw can locally keep all needed information up to
date via netdev_event().
But it seems the netdev itself can change during the lifetime of
a siw device? With that ifindex would become wrong.
If the netdev can change without the siw driver being informed,
holding a netdev pointer or reference seems useless.
So it would be best to always use ib_device_get_netdev() to get
a valid netdev pointer, if current netdev info is needed by the
driver?
I just wanted to avoid the costly ib_device_get_netdev() call
during query_qp(), query_port() and listen().
Thank you!
Bernard.
