NFSv4: More CLOSE/OPEN races

If an OPEN RPC call races with a CLOSE or OPEN_DOWNGRADE so that it
updates the nfs_state structure before the CLOSE/OPEN_DOWNGRADE has
a chance to do so, then we know that the state->flags need to be
recalculated from scratch.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/nfs4proc.c

@@ -1167,6 +1167,16 @@ static bool nfs_need_update_open_stateid(struct nfs4_state *state,
 	return false;
 }
 
+static void nfs_resync_open_stateid_locked(struct nfs4_state *state)
+{
+	if (state->n_wronly)
+		set_bit(NFS_O_WRONLY_STATE, &state->flags);
+	if (state->n_rdonly)
+		set_bit(NFS_O_RDONLY_STATE, &state->flags);
+	if (state->n_rdwr)
+		set_bit(NFS_O_RDWR_STATE, &state->flags);
+}
+
 static void nfs_clear_open_stateid_locked(struct nfs4_state *state,
 		nfs4_stateid *stateid, fmode_t fmode)
 {
@@ -1185,8 +1195,12 @@ static void nfs_clear_open_stateid_locked(struct nfs4_state *state,
 	}
 	if (stateid == NULL)
 		return;
-	if (!nfs_need_update_open_stateid(state, stateid))
+	/* Handle races with OPEN */
+	if (!nfs4_stateid_match_other(stateid, &state->open_stateid) ||
+	    !nfs4_stateid_is_newer(stateid, &state->open_stateid)) {
+		nfs_resync_open_stateid_locked(state);
 		return;
+	}
 	if (test_bit(NFS_DELEGATED_STATE, &state->flags) == 0)
 		nfs4_stateid_copy(&state->stateid, stateid);
 	nfs4_stateid_copy(&state->open_stateid, stateid);