NFS handle COPY ERR_OFFLOAD_NO_REQS

If client sent async COPY and server replied with
ERR_OFFLOAD_NO_REQS, client should retry with a synchronous copy.

Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/nfs42proc.c

@@ -316,7 +316,11 @@ ssize_t nfs42_proc_copy(struct file *src, loff_t pos_src,
 		if (err == -ENOTSUPP) {
 			err = -EOPNOTSUPP;
 			break;
-		} if (err == -EAGAIN) {
+		} else if (err == -EAGAIN) {
+			dst_exception.retry = 1;
+			continue;
+		} else if (err == -NFS4ERR_OFFLOAD_NO_REQS && !args.sync) {
+			args.sync = true;
 			dst_exception.retry = 1;
 			continue;
 		}