md: ensure changes to 'write-mostly' are reflected in metadata.

The 'write-mostly' flag can be changed through sysfs.
With 0.90 metadata, those changes are reflected in the metadata.
For 1.x metadata, they aren't.

So fix super_1_sync to record 'write-mostly' status.

Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 1cd9bfb45e9a..9a880239219d 100644
--- a/drivers/md/md.c
+++ b/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);