knfsd: allow cache_register to return error on failure

Newer server features such as nfsv4 and gss depend on proc to work, so a
failure to initialize the proc files they need should be treated as
fatal.

Thanks to Andrew Morton for style fix and compile fix in case where
CONFIG_NFSD_V4 is undefined.

Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

fs/nfsd/nfs4idmap.c

@@ -464,11 +464,18 @@ nametoid_update(struct ent *new, struct ent *old)
  * Exported API
  */
 
-void
+int
 nfsd_idmap_init(void)
 {
-	cache_register(&idtoname_cache);
-	cache_register(&nametoid_cache);
+	int rv;
+
+	rv = cache_register(&idtoname_cache);
+	if (rv)
+		return rv;
+	rv = cache_register(&nametoid_cache);
+	if (rv)
+		cache_unregister(&idtoname_cache);
+	return rv;
 }
 
 void