net: dccp: fix kernel crash on module load

Patch eedbbb0d98b2 "net: dccp: initialize (addr,port) ..."
added calling to inet_hashinfo2_init() from dccp_init().

However, inet_hashinfo2_init() is marked as __init(), and
thus the kernel panics when dccp is loaded as module. Removing
__init() tag from inet_hashinfo2_init() is not feasible because
it calls into __init functions in mm.

This patch adds inet_hashinfo2_init_mod() function that can
be called after the init phase is done; changes dccp_init() to
call the new function; un-marks inet_hashinfo2_init() as
exported.

Fixes: eedbbb0d98b2 ("net: dccp: initialize (addr,port) ...")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Peter Oskolkov <posk@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index be0b223..2cc5fbb 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -1139,11 +1139,11 @@ static int __init dccp_init(void)
 	rc = percpu_counter_init(&dccp_orphan_count, 0, GFP_KERNEL);
 	if (rc)
 		goto out_fail;
-	rc = -ENOBUFS;
 	inet_hashinfo_init(&dccp_hashinfo);
-	inet_hashinfo2_init(&dccp_hashinfo, "dccp_listen_portaddr_hash",
-			    INET_LHTABLE_SIZE, 21,  /* one slot per 2 MB*/
-			    0, 64 * 1024);
+	rc = inet_hashinfo2_init_mod(&dccp_hashinfo);
+	if (rc)
+		goto out_fail;
+	rc = -ENOBUFS;
 	dccp_hashinfo.bind_bucket_cachep =
 		kmem_cache_create("dccp_bind_bucket",
 				  sizeof(struct inet_bind_bucket), 0,