[dm-devel] dm-cache invalidate_cblocks range parsing

[Alasdair G Kergon]

On Sun, Nov 24, 2013 at 02:25:33AM +0000, Mears, Morgan wrote:
> 	dmsetup message cache 0 invalidate_cblocks 10-11
> cblock 11 will still be in the cache.  

I think that should be changed.

It runs counter to the way LVM handles range specifications and seems
set to create avoidable ambiguity: everyone looking at any ranges in
dm/lvm would now have to check whether the last item in a range is
included or not in each context they encounter one as we would no longer
present a consistent position on this.

To my mind, 10-11 expands to the list of integer block labels consisting 
of 10 and 11,  (We are not talking about intervals pulled out of a
continuous number line here: 10-10.9 would have no meaning.)  I consider
blocks to be discrete objects and saying "the last numbered block listed
is always excluded" strikes me as counter-intuitive.

The compromise we reached for dm statistics to reduce the chance of
misinterpretation was to use start+number_of_items: so 10+1 in this case
where only one block was meant to be included.

Alasdair