[lvm-devel] [PATCH 3/7] Remove snapshot_count from VG and use function instead.

[Alasdair G Kergon]

On Sun, May 10, 2009 at 08:41:32PM +0200, Peter Rockai wrote:
> Patch looks good. Good to get rid of redundant counter, which is prone to
> getting out of sync. I would, however, propose to rename "snapshot_lvs_in_vg"
> to "vg_snapshot_lv_count" -- we already have "vg_missing_pv_count" as a
> precedent for that naming scheme.

Ack.

> PS: I would welcome a similar approach to removing lv_count as well (and other
> redundant counters), since the counting function's implementation clearly
> defines what gets counted in the given counter (vg_lv_count, say), *and* it
> never gets out of sync. In other words, I believe this approach is much more
> transparent, albeit a little less efficient -- however, I don't believe such
> counting function is going to show up on any profile of any LVM2 command
> whatsoever.

If it ever did, we could just optimise things by putting it back in:-)
It's only needed for display tools (and there are caching tricks we could use
there but don't) and the tiny subset of people these days who found a use for
max_lv (or don't need it but are running systems that inherited it from LVM1).
 
Alasdair