Re: [PATCH net-next v2 2/2] bonding: combine netlink and console error messages

[Jonathan Toppins]

On 8/11/21 9:23 AM, Joe Perches wrote:
> On Wed, 2021-08-11 at 05:49 -0700, Jakub Kicinski wrote:
> > On Tue, 10 Aug 2021 20:27:01 -0700 Joe Perches wrote:
> > > > +#define BOND_NL_ERR(bond_dev, extack, errmsg) do {		\
> > > > +	if (extack)						\
> > > > +		NL_SET_ERR_MSG(extack, errmsg);			\
> > > > +	else							\
> > > > +		netdev_err(bond_dev, "Error: %s\n", errmsg);	\
> > > > +} while (0)
> > > > +
> > > > +#define SLAVE_NL_ERR(bond_dev, slave_dev, extack, errmsg) do {		\
> > > > +	if (extack)							\
> > > > +		NL_SET_ERR_MSG(extack, errmsg);				\
> > > > +	else								\
> > > > +		slave_err(bond_dev, slave_dev, "Error: %s\n", errmsg);	\
> > > > +} while (0)
> > >
> > > Ideally both of these would be static functions and not macros.
> >
> > That may break our ability for NL_SET_ERR_MSG to place strings
> > back in a static buffer, no?
>
> Not really.
>
> The most common way to place things in a particular section is to
> use __section("whatever")
>
> It's pretty trivial to mark these errmsg strings as above.

I am unable to convert these to functions at this time, due to how 
NL_SET_ERR_MSG is expanded. This is with either a param list prototype 
of, "const char *errmsg" or "const char errmsg[]".

$ make C=1 drivers/net/bonding/bonding.ko
  CALL    scripts/checksyscalls.sh
  CALL    scripts/atomic/check-atomics.sh
  DESCEND objtool
  DESCEND bpf/resolve_btfids
  CC [M]  drivers/net/bonding/bond_main.o
In file included from ./include/uapi/linux/neighbour.h:6,
                 from ./include/linux/netdevice.h:45,
                 from ./include/net/inet_sock.h:19,
                 from ./include/net/ip.h:28,
                 from drivers/net/bonding/bond_main.c:42:
drivers/net/bonding/bond_main.c: In function ‘bond_nl_err’:
drivers/net/bonding/bond_main.c:1733:26: error: invalid initializer
   NL_SET_ERR_MSG(extack, errmsg);
                          ^~~~~~
./include/linux/netlink.h:92:30: note: in definition of macro 
‘NL_SET_ERR_MSG’
  static const char __msg[] = msg;  \
                              ^~~
drivers/net/bonding/bond_main.c: In function ‘slave_nl_err’:
drivers/net/bonding/bond_main.c:1744:26: error: invalid initializer
   NL_SET_ERR_MSG(extack, errmsg);
                          ^~~~~~
./include/linux/netlink.h:92:30: note: in definition of macro 
‘NL_SET_ERR_MSG’
  static const char __msg[] = msg;  \
                              ^~~
make[3]: *** [scripts/Makefile.build:271: 
drivers/net/bonding/bond_main.o] Error 1
make[2]: *** [scripts/Makefile.build:514: drivers/net/bonding] Error 2
make[1]: *** [scripts/Makefile.build:514: drivers/net] Error 2
make: *** [Makefile:1841: drivers] Error 2