On Mon, Mar 4, 2019 at 10:00 PM Christian Brauner <christ...@brauner.io> wrote:
>
> On Mon, Mar 04, 2019 at 09:38:03PM +0100, Arnd Bergmann wrote:
> > When CONFIG_SYSCTL is turned off, we get a link failure for
> > the newly introduced tuning knob.
> >
> > net/ipv6/addrconf.o: In function `addrconf_init_net':
> > addrconf.c:(.text+0x31dc): undefined reference to
> > `sysctl_devconf_inherit_init_net'
> >
> > Add an IS_ENABLED() check to fall back to the default behavior
> > (sysctl_devconf_inherit_init_net=0) here.
> >
> > Fixes: 856c395cfa63 ("net: introduce a knob to control whether to inherit
> > devconf config")
> > Signed-off-by: Arnd Bergmann <a...@arndb.de>
> > ---
> > net/ipv4/devinet.c | 4 +++-
> > net/ipv6/addrconf.c | 3 ++-
> > 2 files changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> > index cd9033245b98..eb514f312e6f 100644
> > --- a/net/ipv4/devinet.c
> > +++ b/net/ipv4/devinet.c
> > @@ -2614,7 +2614,9 @@ static __net_init int devinet_init_net(struct net
> > *net)
> > tbl[0].extra2 = net;
> > #endif
> >
> > - if (sysctl_devconf_inherit_init_net != 2 && !net_eq(net, &init_net)) {
> > + if ((!IS_ENABLED(CONFIG_SYSCTL) ||
> > + sysctl_devconf_inherit_init_net != 2) &&
>
> I'm sure I'm just being stupid here but wouldn't this still trigger the
> warning or is sysctl_devconf_inherit_init_net unconditionally defined?
> The error you're reporting makes it look like it isn't.
The declaration is unconditional in include/linux/netdevice.h, so the
compiler does not see a problem, it simply doesn't create a reference
when it sees that the code path is dead.
The error message I quoted is from the linker, so this is in turn
not a problem after there is no reference to the variable.
Arnd
