> Or allocate i[t] on stack, but I don't know of any way to
> allocate a variable size on stack (I don't think alloca is allowed in
> kernel). 
I see what I think is a non-standard gcc extension at uvm_pager.c:294
in uvm_aio_aiodone():

	struct vm_page *pg, *pgs[npages];

This, from rev 1.59 of uvm_pager.c.  It crops up in uvm_bio.c v1.26, too.
Is this usage...acceptable?  If so, well, there you go: variable-sized arrays.

If it's not OK, well, what's wrong with relying
on some features of the bundled compiler?

> Manuel Bouyer <bouyer@antioche.eu.org>
Chris <jepeway@blasted-heath.com>.