i have a mazda 6 diesel and have exactly the same problem at service time. is your dpf light flashing or on all the time?
ive also heard that the dpf light starts flashing on mazda 6 diesels when the service is due and is reset when you take it back to mazda.
The DPF light is off and then starts flashing, at no time is it on all the time.
The first time it happened was a few months after I’d had it serviced at a indy garage.
Both times were roughly about when a service was due, this and the fact there was no noticable difference in the way the car was running makes me suspect it may be a fleecing exercise, but if the manual says get it to a dealer ASAP and the internet forums are full of people who have lost engines, what do u do?