Linux Ethernet Bridging - Feb 2021 - [Bridge] [PATCH v2 net-next 03/11] net: bridge: don't print in br_switchdev_set_port_flag

On Tue, Feb 09, 2021 at 05:19:28PM +0200, Vladimir Oltean
wrote:
> From: Vladimir Oltean <vladimir.oltean at nxp.com>
>
> Currently br_switchdev_set_port_flag has two options for error handling
> and neither is good:
> - The driver returns -EOPNOTSUPP in PRE_BRIDGE_FLAGS if it doesn't
>   support offloading that flag, and this gets silently ignored and
>   converted to an errno of 0. Nobody does this.
> - The driver returns some other error code, like -EINVAL, in
>   PRE_BRIDGE_FLAGS, and br_switchdev_set_port_flag shouts loudly.
>
> The problem is that we'd like to offload some port flags during bridge
> join and leave, but also not have the bridge shout at us if those fail.
> But on the other hand we'd like the user to know that we can't
offload
> something when they set that through netlink. And since we can't have
> the driver return -EOPNOTSUPP or -EINVAL depending on whether it's
> called by the user or internally by the bridge, let's just add an
extack
> argument to br_switchdev_set_port_flag and propagate it to its callers.
> Then, when we need offloading to really fail silently, this can simply
> be passed a NULL argument.
>
> Signed-off-by: Vladimir Oltean <vladimir.oltean at nxp.com>
> ---
The build fails because since I started working on v2 and until I sent
it, Jakub merged net into net-next which contained this fix:
https://patchwork.kernel.org/project/netdevbpf/patch/20210207194733.1811529-1-olteanv
at gmail.com/
for which I couldn't change prototype due to it missing in net-next.
I think I would like to rather wait to gather some feedback first before
respinning v3, if possible.

On Tue, Feb 09, 2021 at 07:36:31PM +0200, Vladimir Oltean
wrote:
> On Tue, Feb 09, 2021 at 05:19:28PM +0200, Vladimir Oltean wrote:
> > From: Vladimir Oltean <vladimir.oltean at nxp.com>
> >
> > Currently br_switchdev_set_port_flag has two options for error
handling
> > and neither is good:
> > - The driver returns -EOPNOTSUPP in PRE_BRIDGE_FLAGS if it doesn't
> >   support offloading that flag, and this gets silently ignored and
> >   converted to an errno of 0. Nobody does this.
> > - The driver returns some other error code, like -EINVAL, in
> >   PRE_BRIDGE_FLAGS, and br_switchdev_set_port_flag shouts loudly.
> >
> > The problem is that we'd like to offload some port flags during
bridge
> > join and leave, but also not have the bridge shout at us if those
fail.
> > But on the other hand we'd like the user to know that we can't
offload
> > something when they set that through netlink. And since we can't
have
> > the driver return -EOPNOTSUPP or -EINVAL depending on whether it's
> > called by the user or internally by the bridge, let's just add an
extack
> > argument to br_switchdev_set_port_flag and propagate it to its
callers.
> > Then, when we need offloading to really fail silently, this can simply
> > be passed a NULL argument.
> >
> > Signed-off-by: Vladimir Oltean <vladimir.oltean at nxp.com>
> > ---
> 
> The build fails because since I started working on v2 and until I sent
> it, Jakub merged net into net-next which contained this fix:
>
https://patchwork.kernel.org/project/netdevbpf/patch/20210207194733.1811529-1-olteanv
at gmail.com/
> for which I couldn't change prototype due to it missing in net-next.
> I think I would like to rather wait to gather some feedback first before
> respinning v3, if possible.
It seems that in the sysfs call path br_switchdev_set_port_flag() will
be called with the bridge lock held, which is going to be a problem
given that patch #8 allows this function to block.