[PATCH-next,v3] netfilter: don't use module_init/exit in core IPV4 code

The file net/ipv4/netfilter.o is created based on whether
CONFIG_NETFILTER is set.  However that is defined as a bool, and
hence this file with the core netfilter hooks will never be
modular.  So using module_init as an alias for __initcall can be
somewhat misleading.

Fix this up now, so that we can relocate module_init from
init.h into module.h in the future.  If we don't do this, we'd
have to add module.h to obviously non-modular code, and that
would be a worse thing.  Also add an inclusion of init.h, as
that was previously implicit here in the netfilter.c file.

Note that direct use of __initcall is discouraged, vs. one
of the priority categorized subgroups.  As __initcall gets
mapped onto device_initcall, our use of subsys_initcall (which
seems to make sense for netfilter code) will thus change this
registration from level 6-device to level 4-subsys (i.e. slightly
earlier).  However no observable impact of that small difference
has been observed during testing, or is expected. (i.e. the
location of the netfilter messages in dmesg remains unchanged
with respect to all the other surrounding messages.)

As for the module_exit, rather than replace it with __exitcall,
we simply remove it, since it appears only UML does anything
with those, and even for UML, there is no relevant cleanup
to be done here.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---

[v3: switch accidental device_initcall back to subsys_initcall
 as spotted by Benjamin Poirier; retest on ppc-sbc8548 net-next]

[v2: Drop __exitcall stuff completely, as per Eric's suggestion
 given for patch at  http://patchwork.ozlabs.org/patch/311164/ ]

 net/ipv4/netfilter.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

On Thu, Jan 16, 2014 at 03:24:03PM -0500, Paul Gortmaker wrote:
> The file net/ipv4/netfilter.o is created based on whether
> CONFIG_NETFILTER is set.  However that is defined as a bool, and
> hence this file with the core netfilter hooks will never be
> modular.  So using module_init as an alias for __initcall can be
> somewhat misleading.
> 
> Fix this up now, so that we can relocate module_init from
> init.h into module.h in the future.  If we don't do this, we'd
> have to add module.h to obviously non-modular code, and that
> would be a worse thing.  Also add an inclusion of init.h, as
> that was previously implicit here in the netfilter.c file.
> 
> Note that direct use of __initcall is discouraged, vs. one
> of the priority categorized subgroups.  As __initcall gets
> mapped onto device_initcall, our use of subsys_initcall (which
> seems to make sense for netfilter code) will thus change this
> registration from level 6-device to level 4-subsys (i.e. slightly
> earlier).  However no observable impact of that small difference
> has been observed during testing, or is expected. (i.e. the
> location of the netfilter messages in dmesg remains unchanged
> with respect to all the other surrounding messages.)
> 
> As for the module_exit, rather than replace it with __exitcall,
> we simply remove it, since it appears only UML does anything
> with those, and even for UML, there is no relevant cleanup
> to be done here.

Just to bring up the idea: there's no reason why we couldn't make
netfilter fully modular for individual AFs. I've seen quite a lot
of embedded systems that include the IPv6 netfilter core without
using it.

Its rather complicated to get all the dependencies of xtables
modules right though, so this is really just to bring up the
idea.

Your patch looks fine to me.
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