NFS4: Set security flavor default for NFSv4 mounts like other defaults

Set the default security flavor when we set the other mount option
default values for NFSv4.  This cleans up the NFSv4 mount option parsing
path to look like the NFSv2/v3 one.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/super.c

@@ -2125,6 +2125,8 @@ static int nfs4_validate_mount_data(void *options,
 	args->acdirmin		= NFS_DEF_ACDIRMIN;
 	args->acdirmax		= NFS_DEF_ACDIRMAX;
 	args->nfs_server.port	= NFS_PORT; /* 2049 unless user set port= */
+	args->auth_flavors[0]	= RPC_AUTH_UNIX;
+	args->auth_flavor_len	= 0;
 
 	switch (data->version) {
 	case 1:
@@ -2140,18 +2142,13 @@ static int nfs4_validate_mount_data(void *options,
 						&args->nfs_server.address))
 			goto out_no_address;
 
-		switch (data->auth_flavourlen) {
-		case 0:
-			args->auth_flavors[0] = RPC_AUTH_UNIX;
-			break;
-		case 1:
+		if (data->auth_flavourlen) {
+			if (data->auth_flavourlen > 1)
+				goto out_inval_auth;
 			if (copy_from_user(&args->auth_flavors[0],
 					   data->auth_flavours,
 					   sizeof(args->auth_flavors[0])))
 				return -EFAULT;
-			break;
-		default:
-			goto out_inval_auth;
 		}
 
 		c = strndup_user(data->hostname.data, NFS4_MAXNAMLEN);
@@ -2203,15 +2200,8 @@ static int nfs4_validate_mount_data(void *options,
 
 		nfs_validate_transport_protocol(args);
 
-		switch (args->auth_flavor_len) {
-		case 0:
-			args->auth_flavors[0] = RPC_AUTH_UNIX;
-			break;
-		case 1:
-			break;
-		default:
+		if (args->auth_flavor_len > 1)
 			goto out_inval_auth;
-		}
 
 		if (args->client_address == NULL)
 			goto out_no_client_address;