NFSv4: Fix a regression in nfs_set_open_stateid_locked()

If we already hold open state on the client, yet the server gives us a
completely different stateid to the one we already hold, then we
currently treat it as if it were an out-of-sequence update, and wait for
5 seconds for other updates to come in.
This commit fixes the behaviour so that we immediately start processing
of the new stateid, and then leave it to the call to
nfs4_test_and_free_stateid() to decide what to do with the old stateid.

Fixes: b4868b44 ("NFSv4: Wait for stateid updates after CLOSE/OPEN_DOWNGRADE")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/nfs4proc.c

@@ -1604,15 +1604,16 @@ static bool nfs_stateid_is_sequential(struct nfs4_state *state,
 {
 	if (test_bit(NFS_OPEN_STATE, &state->flags)) {
 		/* The common case - we're updating to a new sequence number */
-		if (nfs4_stateid_match_other(stateid, &state->open_stateid) &&
-			nfs4_stateid_is_next(&state->open_stateid, stateid)) {
-			return true;
+		if (nfs4_stateid_match_other(stateid, &state->open_stateid)) {
+			if (nfs4_stateid_is_next(&state->open_stateid, stateid))
+				return true;
+			return false;
 		}
-	} else {
-		/* This is the first OPEN in this generation */
-		if (stateid->seqid == cpu_to_be32(1))
-			return true;
+		/* The server returned a new stateid */
 	}
+	/* This is the first OPEN in this generation */
+	if (stateid->seqid == cpu_to_be32(1))
+		return true;
 	return false;
 }