dm persistent data: fix shadow_info_leak on dm_tm_destroy

commit 25d7cd6f upstream.

Cleanup the shadow table before destroying the transaction manager.

Reference: leak was identified with kmemleak when running
test_discard_random_sectors in the thinp-test-suite.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/md/persistent-data/dm-transaction-manager.c

@@ -138,6 +138,9 @@ EXPORT_SYMBOL_GPL(dm_tm_create_non_blocking_clone);
 
 void dm_tm_destroy(struct dm_transaction_manager *tm)
 {
+	if (!tm->is_clone)
+		wipe_shadow_table(tm);
+
 	kfree(tm);
 }
 EXPORT_SYMBOL_GPL(dm_tm_destroy);