30A. Current in series remains the same, only voltages add. (in parallel it is the opposite).
However, if the discharge FETs (and charge FETs, if those are also seriesed) are not rated higher than the full total series voltage of both packs (and any voltage spikes that happen from the motor system during this event), then as soon as either BMS shuts off the FETs (for instance, to protect against a low cell being overdischarged), the full total voltage will be across just that single BMS's FETs, and they'll fail from overvoltage.
A common failure mode is shorted (stuck on), so rather than a power loss event, the system may appear to continue to operate normally, but since the BMS was trying to shut down to protect the cells against a potentially destructive situation, but can't, that situation may now happen.
For instance, if a cell had run low (empty), it will now continue to be discharged (instead of being protected) and may reverse voltage from the current flow thru it, which is a fairly bad thing to do to a cell.
As long as the FETs are rated for a high enough voltage, then nothing bad should happen...but if they're not....
Additionally, your controller will need to do the current limiting to the *least* current handling ability par of the system. So not just to what the motor can handle, but also to what the battery can handle.
If the battery can only handle 30A maximum then the controller must be setup to not draw more than 30A in it's battery current limit settings (preferably less, to not push the battery to it's limits, which will give the battery a longer lifespan).
If the motor can only handle 34A phase current, then the controller must be setup to not allow the motor to draw more than 34A phase current. Note that the motor can still be damaged by overheating if it is drawing high phase currents at low RPM for a long enough time.