NFSv4.1: Allow getdeviceinfo to return notification info back to caller

We are only allowed to cache deviceinfo if the server supports notifications
and actually promises to call us back when changes occur. Right now, we
request those notifications, but then we don't check the server's reply.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 627f37c..ba8b2b5 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -7944,6 +7944,8 @@
 {
 	struct nfs4_getdeviceinfo_args args = {
 		.pdev = pdev,
+		.notify_types = NOTIFY_DEVICEID4_CHANGE |
+			NOTIFY_DEVICEID4_DELETE,
 	};
 	struct nfs4_getdeviceinfo_res res = {
 		.pdev = pdev,
@@ -7958,6 +7960,9 @@
 
 	dprintk("--> %s\n", __func__);
 	status = nfs4_call_sync(server->client, server, &msg, &args.seq_args, &res.seq_res, 0);
+	if (res.notification & ~args.notify_types)
+		dprintk("%s: unsupported notification\n", __func__);
+
 	dprintk("<-- %s status=%d\n", __func__, status);
 
 	return status;