>How do other OS manage this, e.g. Solaris? (It seems Linux doesn't support
	>this, at least I can't find any mention of aio in 2.3.49 kernel sources).

ISTR solaris uses a different driver entry point for aio and does not
biowait().  Instead, there is a kernel aio structure/process to keep
track of pending I/Os, and waiting is done on that structure only
when the process specifically desires to wait for I/O completion.

However, it has been quite a while since I was messing around with
that code, so my memory may not be all that accurate.

Eduardo