nfs41: Allow NFSv4 and NFSv4.1 callback services to coexist

Tracks the nfs_callback_info for both versions, enabling the callback
service for v4 and v4.1 to run concurrently and be stopped independently
of each other.

Signed-off-by: Ricardo Labiaga <ricardo.labiaga@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
diff --git a/fs/nfs/callback.h b/fs/nfs/callback.h
index 29123b5..88d2e11 100644
--- a/fs/nfs/callback.h
+++ b/fs/nfs/callback.h
@@ -64,11 +64,8 @@
 
 #ifdef CONFIG_NFS_V4
 extern int nfs_callback_up(u32 minorversion, struct rpc_xprt *xprt);
-extern void nfs_callback_down(void);
-#else
-#define nfs_callback_up()	(0)
-#define nfs_callback_down()	do {} while(0)
-#endif
+extern void nfs_callback_down(int minorversion);
+#endif /* CONFIG_NFS_V4 */
 
 /*
  * nfs41: Callbacks are expected to not cause substantial latency,