Rerolling 1 and 2 but only once?

The fighter fighting style great weapon master requires that when you roll a 1 or 2 on damage dice you can reroll them but must take it even if its a 1 or 2. Using the roll20 system one can say /roll 2d6r<2 but the problem is it rerolls 1 and 2s even after it rerolls them. So it could go on endlessly if you got unlucky enough. Is there a specific command to make this work or do you have to just do this specific one manually.

Put an "o" after the "r" for "re-roll once" /roll 2d6ro<2 You can explore the dice rolling options and syntax available here on the wiki. Re-rolling modifiers here .