Sample Block Multiqueue Driver

[cdupuis1 at gmail.com]

Hi Folks,

While there are some good references for block drivers such as loop and
null_blk, I've not see a good bare bones block multiqueue example
driver.  This may not mean that one doesn't exist but since I
personally have not seen one, I've created one called blk_example which
I've posted on my github account: 
https://github.com/cdupuis1/nvme_test/tree/master/blk_example.

I've tried to make as bare bones a driver that actually still will work
as a small block device, /dev/blk_example.  The memory footprint of the
backing store is relatively small, 2000 sectors or 1MB, but is
resizeable with the num_sectors module parameter.

It was helpful as a learning experience for me so I'd thought I would
share in case anyone else happened to be looking for such a sample
driver.  Comments or improvements are welcome.

Thanks,
Chad