NFSD: Skip close replay processing if XDR encoding fails

The replay logic added by commit 9411b1d ("nfsd4: cleanup
handling of nfsv4.0 closed stateid's") cannot be done if encoding
failed due to a short send buffer; there's no guarantee that the
operation encoder has actually encoded the data that is being copied
to the replay cache.

Reported-by: rtm@csail.mit.edu
Closes: https://lore.kernel.org/linux-nfs/c3628d57-94ae-48cf-8c9e-49087a28cec9@oracle.com/T/#t
Fixes: 9411b1d ("nfsd4: cleanup handling of nfsv4.0 closed stateid's")
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Author: chucklever

fs/nfsd/nfs4xdr.c

@@ -5925,8 +5925,7 @@ nfsd4_encode_operation(struct nfsd4_compoundres *resp, struct nfsd4_op *op)
 		 */
 		warn_on_nonidempotent_op(op);
 		xdr_truncate_encode(xdr, op_status_offset + XDR_UNIT);
-	}
-	if (so) {
+	} else if (so) {
 		int len = xdr->buf->len - (op_status_offset + XDR_UNIT);
 
 		so->so_replay.rp_status = op->status;