This patch prevents memory corruption from "rmmod nbd" with the existing 
2.5.72 (and earlier) nbd driver. It does this by updating the nbd driver 
to the new block layer requirement that every disk has its own 
request_queue structure. This is the first of a series of patchlets 
designed to break down the essential changes I proposed in my last 
"enormous" patch. Note that another patchlet will make the whole 
allocation of per nbd_device memory be dynamic (rather than staticly 
tied to MAX_NBD). Please try out this patch and let me know how nbd is 
working for you before versus after. With any luck, some of these 
smaller patch breakdowns can actually see there way into new kernel 
releases. Thanks.