Re: [PATCH 1/3] ifb: make device count build-time configurable

[Daniel Borkmann]

On 01/12/2016 04:19 PM, Daniel Borkmann wrote:
> On 01/12/2016 12:56 PM, Lubomir Rintel wrote:
> > The devices can be created at run-time for quite some time already and the
> > load-time device creation collides with attempts to create the device of
> > the same name:
> >
> >    # rmmod ifb
> >    # ip link add ifb0 type ifb
> >    RTNETLINK answers: File exists
> >
> > This is pretty much the same situation as was with the block loop devices
> > which was solved by adding a build-time configuration that the
> > distributions could use as they deem fit while keeping the default for
> > compatibility.
> >
> > Let's do that here as well.
>
> Thanks for the set in general, good to see it fixed!
>
> > Signed-off-by: Lubomir Rintel <lkundrak@xxxxx>
> > ---
> [...]
> > +config IFB_COUNT
> > +        int "Number of ifb devices to pre-create at init time"
> > +        depends on IFB
> > +        default 3
>
> Should that not be 2?
>
> > +        help
> > +          Static number of ifb devices to be unconditionally pre-created
> > +          at init time.
> > +
> > +          This default value can be overwritten on the kernel command
> > +          line or with module-parameter ifb.numifbs.
> > +
> > +          The historic default is 3. If a mid-2007 version of iproute2
> > +          is used (v2.6.23 or later), it can be set to 0, since needed
> > +          ifb devices can be dynamically allocated via rtnetlink.
>
> [...]
> > -static int numifbs = 2;
>                ^^^^^^^^^^^^
> > +static int numifbs = CONFIG_IFB_COUNT;
> >   module_param(numifbs, int, 0);
> >   MODULE_PARM_DESC(numifbs, "Number of ifb devices");

Btw, perhaps there should also be a pr_info() or the like to warn the user
that relying on modprobe creating these devs is deprecated and scheduled
for removal in future, so they should switch to ip link instead ...