dm raid: add support for resync w/o metadata devices

Target does not honour the "sync" argument when activated w/o metadata
devices, e.g. with table line:
"0 $(blockdev --getsz $data1) raid raid1 2 0 sync 2 - $data1 - $data2".

Fix this to support temporary, transient raid devices useful
for data duplication.

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

Author: mauelsha

drivers/md/dm-raid.c

@@ -2532,6 +2532,10 @@ static int analyse_superblocks(struct dm_target *ti, struct raid_set *rs)
 	struct md_rdev *rdev, *freshest;
 	struct mddev *mddev = &rs->md;
 
+	/* Respect resynchronization requested with "sync" argument. */
+	if (test_bit(__CTR_FLAG_SYNC, &rs->ctr_flags))
+		set_bit(MD_ARRAY_FIRST_USE, &mddev->flags);
+
 	freshest = NULL;
 	rdev_for_each(rdev, mddev) {
 		if (test_bit(Journal, &rdev->flags))