diff --git a/[refs] b/[refs]
index 161c2b53a369..12f570a2a7b8 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 5ef56c8fecedf403a346d02140e52a072d693d6b
+refs/heads/master: aeb9b211849621f592288ed5ad694de9eeaae87a
diff --git a/trunk/drivers/md/md.c b/trunk/drivers/md/md.c
index 1cd9bfb45e9a..9a880239219d 100644
--- a/trunk/drivers/md/md.c
+++ b/trunk/drivers/md/md.c
@@ -1738,6 +1738,11 @@ static void super_1_sync(mddev_t *mddev, mdk_rdev_t *rdev)
 	sb->level = cpu_to_le32(mddev->level);
 	sb->layout = cpu_to_le32(mddev->layout);
 
+	if (test_bit(WriteMostly, &rdev->flags))
+		sb->devflags |= WriteMostly1;
+	else
+		sb->devflags &= ~WriteMostly1;
+
 	if (mddev->bitmap && mddev->bitmap_info.file == NULL) {
 		sb->bitmap_offset = cpu_to_le32((__u32)mddev->bitmap_info.offset);
 		sb->feature_map = cpu_to_le32(MD_FEATURE_BITMAP_OFFSET);