Merge tag 'md-3.4-fixes' of git://neil.brown.name/md

Pull a few more md bug fixes from NeilBrown:
"2 are tagged for -stable, one being for a fairly serious bug that can
corrupt metadata and make it hard to recovery an array. The other is
for a more recent regression since 3.3"

* tag 'md-3.4-fixes' of git://neil.brown.name/md:
md: fix possible corruption of array metadata on shutdown.
md: don't call ->add_disk unless there is good reason.
DM RAID: Use safe version of rdev_for_each

drivers/md/dm-raid.c

···
 	int ret;
 	unsigned redundancy = 0;
 	struct raid_dev *dev;
-	struct md_rdev *rdev, *freshest;
+	struct md_rdev *rdev, *tmp, *freshest;
 	struct mddev *mddev = &rs->md;
 
 	switch (rs->raid_type->level) {
···
 	}
 
 	freshest = NULL;
-	rdev_for_each(rdev, mddev) {
+	rdev_for_each_safe(rdev, tmp, mddev) {
 		if (!rdev->meta_bdev)
 			continue;
 

drivers/md/md.c

···
 		 * any transients in the value of "sync_action".
 		 */
 		set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
-		clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
 		/* Clear some bits that don't mean anything, but
 		 * might be left set
 		 */
 		clear_bit(MD_RECOVERY_INTR, &mddev->recovery);
 		clear_bit(MD_RECOVERY_DONE, &mddev->recovery);
 
-		if (test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
+		if (!test_and_clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery) ||
+		    test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
 			goto unlock;
 		/* no recovery is running.
 		 * remove any failed drives, then
···
 
 	for_each_mddev(mddev, tmp) {
 		if (mddev_trylock(mddev)) {
-			__md_stop_writes(mddev);
+			if (mddev->pers)
+				__md_stop_writes(mddev);
 			mddev->safemode = 2;
 			mddev_unlock(mddev);
 		}