For the past few years David Mamet has played both sides against the middle, churning out forgettable genre pictures (Heist, Spartan) and excusing himself with cranky screeds against the movie industry (culminating in his 2007 book Bambi vs. Godzilla). A triumphant return to form, Redbelt combines both impulses. It’s a classic fight movie, with Chiwetel Ejiofor as an honorable martial arts instructor whose money problems force him into the ring for a hyped TV match. But nesting inside is a sour little 70s-style David Mamet play about the lies, calculations, and ice-cold politics of Hollywood, as the fighter is befriended and then discarded by a callow movie star (Tim Allen). The excellent cast includes Alice Braga, Emily Mortimer, Joe Mantegna, Ricky Jay, David Paymer, and Max Martini. R, 99 min.