NFSv4: Ensure we don't re-test revoked and freed stateids

This fixes a potential infinite loop in nfs_reap_expired_delegations.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Tested-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index 0ffead2..484f147 100644
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -656,6 +656,7 @@
 		struct nfs_delegation *delegation)
 {
 	set_bit(NFS_DELEGATION_REVOKED, &delegation->flags);
+	delegation->stateid.type = NFS4_INVALID_STATEID_TYPE;
 	nfs_mark_return_delegation(server, delegation);
 }
 
@@ -894,6 +895,8 @@
 static void nfs_mark_test_expired_delegation(struct nfs_server *server,
 	    struct nfs_delegation *delegation)
 {
+	if (delegation->stateid.type == NFS4_INVALID_STATEID_TYPE)
+		return;
 	clear_bit(NFS_DELEGATION_NEED_RECLAIM, &delegation->flags);
 	set_bit(NFS_DELEGATION_TEST_EXPIRED, &delegation->flags);
 	set_bit(NFS4CLNT_DELEGATION_EXPIRED, &server->nfs_client->cl_state);