+static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)
+{
+ /* Adding a drive to a linear array allows the array to grow.
+ * It is permitted if the new drive has a matching superblock
+ * already on it, with raid_disk equal to raid_disks.
+ * It is achieved by creating a new linear_private_data structure
+ * and swapping it in in-place of the current one.
+ * The current one is never freed until the array is stopped.
+ * This avoids races.
+ */
+ linear_conf_t *newconf;
+
+ if (rdev->raid_disk != mddev->raid_disks)
+ return -EINVAL;
+
+ newconf = linear_conf(mddev,mddev->raid_disks+1);
+
+ if (!newconf)
+ return -ENOMEM;
+
+ newconf->prev = mddev_to_conf(mddev);
+ mddev->private = newconf;
+ mddev->raid_disks++;
+ mddev->array_size = newconf->array_size;
+ set_capacity(mddev->gendisk, mddev->array_size << 1);
+ return 0;