does the request function block

[Christian Widmer]

does the request function of a bock device driver to be attomic or may it 
block? in the linux device driver 2 it says that it must be attomic and 
may not block. that makes sense to me since it also sais that the bottom-
half of the driver will call the request function too. but this is not realy
nessesery when i remove all request before releasing the io_request_lock.
on the other side block devices like nbd or brbd do send date using a socket
in there request function.

who is right and why?