Max of two txgs

Signed-off-by: Paul Dagnelie <paul.dagnelie@klarasystems.com>

Author: Paul Dagnelie

module/zfs/zio.c

@@ -3319,7 +3319,7 @@ zio_write_gang_block(zio_t *pio, metaslab_class_t *mc)
 	    spa_feature_is_enabled(spa, SPA_FEATURE_DYNAMIC_GANG_HEADER) &&
 	    !spa_feature_is_active(spa, SPA_FEATURE_DYNAMIC_GANG_HEADER)) {
 		dmu_tx_t *tx = dmu_tx_create_assigned(spa->spa_dsl_pool,
-		    spa_syncing_txg(spa) + 1);
+		    MAX(txg, spa_syncing_txg(spa) + 1));
 		dsl_sync_task_nowait(spa->spa_dsl_pool,
 		    zio_update_feature,
 		    (void *)SPA_FEATURE_DYNAMIC_GANG_HEADER, tx);