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>

drivers/md/dm-cache-target.c

@@ -1720,6 +1720,7 @@ static void do_worker(struct work_struct *ws)
 
 		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