nfsd4: fix response size estimation for OP_SEQUENCE

commit d1d84c96 upstream.

We added this new estimator function but forgot to hook it up.  The
effect is that NFSv4.1 (and greater) won't do zero-copy reads.

The estimate was also wrong by 8 bytes.

Fixes: ccae70a9 "nfsd4: estimate sequence response size"
Reported-by: Chuck Lever <chucklever@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

fs/nfsd/nfs4proc.c

@@ -1555,7 +1555,8 @@ static inline u32 nfsd4_rename_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op
 static inline u32 nfsd4_sequence_rsize(struct svc_rqst *rqstp,
 				       struct nfsd4_op *op)
 {
-	return NFS4_MAX_SESSIONID_LEN + 20;
+	return (op_encode_hdr_size
+		+ XDR_QUADLEN(NFS4_MAX_SESSIONID_LEN) + 5) * sizeof(__be32);
 }
 
 static inline u32 nfsd4_setattr_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
@@ -1859,6 +1860,7 @@ static struct nfsd4_operation nfsd4_ops[] = {
 		.op_func = (nfsd4op_func)nfsd4_sequence,
 		.op_flags = ALLOWED_WITHOUT_FH | ALLOWED_AS_FIRST_OP,
 		.op_name = "OP_SEQUENCE",
+		.op_rsize_bop = (nfsd4op_rsize)nfsd4_sequence_rsize,
 	},
 	[OP_DESTROY_CLIENTID] = {
 		.op_func = (nfsd4op_func)nfsd4_destroy_clientid,