Re: [RFC v2 06/16] luo: luo_subsystems: add subsystem registration

[Pasha Tatashin]

> Suggest using guard()() and scoped_guard() throughout this series
> instead of manual lock/unlock and up/down. That will simplify the code
> and reduce the chance of silly bugs where a code path misses an
> unlock/down.

This is an interesting suggestion. I have not really considered using
guard()/scoped_guard(). I personally prefer regular lock/unlock/goto
error, IMO the code is more readable this way, but I may revisit this
in the future. Also, at least in mm guards are not used, i.e.  `git
grep scoped_guard mm` returns no results.