Not sure, but I don't think there should be a fallback for the blit in this
case. This is for map/unmap_renderbuffer after all, and if it asserts in unmap
this means the blit from the rb to some temp buffer was succesful. I see no
reason why it shouldn't be possible to blit it back - it was a rb after all, so
should have all the required alignment, format etc. in the first place.
Some of the examples you listed actually look like they should only really
map/unmap zs buf not color, albeit the fallback might just map/unmap everything
always (IIRC that was actually the case last I checked several years ago, and
sometimes responsible for some huge slowdown compared to some old dri1 code -
you draw a single point with some unsupported setup, and 99.999% of the time
spent in the fallback was just for blitting everything to some buffer and
back). Or could there be a problem if there's not actually a color rb and it
tries to blit that?