NFSv4.1 handle ERR_DELAY error reclaiming locking state on delegation recall

A client should be able to handle getting an ERR_DELAY error
while doing a LOCK call to reclaim state due to delegation being
recalled. This is a transient error that can happen due to server
moving its volumes and invalidating its file location cache and
upon reference to it during the LOCK call needing to do an
expensive lookup (leading to an ERR_DELAY error on a PUTFH).
Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/nfs4proc.c

@@ -7298,7 +7298,12 @@ int nfs4_lock_delegation_recall(struct file_lock *fl, struct nfs4_state *state,
 	err = nfs4_set_lock_state(state, fl);
 	if (err != 0)
 		return err;
-	err = _nfs4_do_setlk(state, F_SETLK, fl, NFS_LOCK_NEW);
+	do {
+		err = _nfs4_do_setlk(state, F_SETLK, fl, NFS_LOCK_NEW);
+		if (err != -NFS4ERR_DELAY)
+			break;
+		ssleep(1);
+	} while (err == -NFS4ERR_DELAY);
 	return nfs4_handle_delegation_recall_error(server, state, stateid, fl, err);
 }