md-cluster: change array_sectors and update size are not supported

Currently, some features are not supported yet,
such as change array_sectors and update size, so
return EINVAL for them and listed it in document.
Reviewed-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NGuoqing Jiang <gqjiang@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

Documentation/md-cluster.txt

@@ -316,3 +316,9 @@ The algorithm is:
  nodes are using the raid which is achieved by lock all bitmap
  locks within the cluster, and also those locks are unlocked
  accordingly.
+
+7. Unsupported features
+
+There are somethings which are not supported by cluster MD yet.
+
+- update size and change array_sectors.

drivers/md/md.c

@@ -4817,6 +4817,10 @@ array_size_store(struct mddev *mddev, const char *buf, size_t len)
 	if (err)
 		return err;
 
+	/* cluster raid doesn't support change array_sectors */
+	if (mddev_is_clustered(mddev))
+		return -EINVAL;
+
 	if (strncmp(buf, "default", 7) == 0) {
 		if (mddev->pers)
 			sectors = mddev->pers->size(mddev, 0, 0);
@@ -6438,6 +6442,10 @@ static int update_size(struct mddev *mddev, sector_t num_sectors)
 	int rv;
 	int fit = (num_sectors == 0);
 
+	/* cluster raid doesn't support update size */
+	if (mddev_is_clustered(mddev))
+		return -EINVAL;
+
 	if (mddev->pers->resize == NULL)
 		return -EINVAL;
 	/* The "num_sectors" is the number of sectors of each device that