nfsd: register pernet ops last, unregister first

These pernet operations may depend on stuff set up or torn down in the
module init/exit functions.  And they may be called at any time in
between.  So it makes more sense for them to be the last to be
registered in the init function, and the first to be unregistered in the
exit function.

In particular, without this, the drc slab is being destroyed before all
the per-net drcs are shut down, resulting in an "Objects remaining in
nfsd_drc on __kmem_cache_shutdown()" warning in exit_nfsd.
Reported-by: Zhi Li <yieli@redhat.com>
Fixes: 3ba75830 "nfsd4: drc containerization"
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfsctl.c

@@ -1522,12 +1522,9 @@ static int __init init_nfsd(void)
 	int retval;
 	printk(KERN_INFO "Installing knfsd (copyright (C) 1996 okir@monad.swb.de).\n");
 
-	retval = register_pernet_subsys(&nfsd_net_ops);
-	if (retval < 0)
-		return retval;
 	retval = register_cld_notifier();
 	if (retval)
-		goto out_unregister_pernet;
+		return retval;
 	retval = nfsd4_init_slabs();
 	if (retval)
 		goto out_unregister_notifier;
@@ -1544,9 +1541,14 @@ static int __init init_nfsd(void)
 		goto out_free_lockd;
 	retval = register_filesystem(&nfsd_fs_type);
 	if (retval)
+		goto out_free_exports;
+	retval = register_pernet_subsys(&nfsd_net_ops);
+	if (retval < 0)
 		goto out_free_all;
 	return 0;
 out_free_all:
+	unregister_pernet_subsys(&nfsd_net_ops);
+out_free_exports:
 	remove_proc_entry("fs/nfs/exports", NULL);
 	remove_proc_entry("fs/nfs", NULL);
 out_free_lockd:
@@ -1559,13 +1561,12 @@ static int __init init_nfsd(void)
 	nfsd4_free_slabs();
 out_unregister_notifier:
 	unregister_cld_notifier();
-out_unregister_pernet:
-	unregister_pernet_subsys(&nfsd_net_ops);
 	return retval;
 }
 
 static void __exit exit_nfsd(void)
 {
+	unregister_pernet_subsys(&nfsd_net_ops);
 	nfsd_drc_slab_free();
 	remove_proc_entry("fs/nfs/exports", NULL);
 	remove_proc_entry("fs/nfs", NULL);
@@ -1575,7 +1576,6 @@ static void __exit exit_nfsd(void)
 	nfsd4_exit_pnfs();
 	unregister_filesystem(&nfsd_fs_type);
 	unregister_cld_notifier();
-	unregister_pernet_subsys(&nfsd_net_ops);
 }
 
 MODULE_AUTHOR("Olaf Kirch <okir@monad.swb.de>");