What do you mean by "unknown"? Are You All Reet? is a Cab Calloway recording from 1941. (Btw, I find it funny how both in the midst of and after Chu Berry's solo the band shouts "Yes, he's all reet!", but they have nothing to say about Dizzy's solo!)
From what i understood in the Gillepsie autobiography, there were some tension between Berry and the veterans of the group and the young Dizzy.