dm cache: fail migrations in the do_worker error path

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 2a156af..75073c8 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -1720,6 +1720,7 @@
 
 		if (commit_if_needed(cache)) {
 			process_deferred_flush_bios(cache, false);
+			process_migrations(cache, &cache->need_commit_migrations, migration_failure);
 
 			/*
 			 * FIXME: rollback metadata or just go into a