[PATCH 1/5] nvme: track subsystems

[Sagi Grimberg]

>> Any reason to do all this before we know if we found an existing subsystem?
> 
> We'd either have to do all the initialization including the memory
> allocation and ida_simple_get under nvme_subsystems_lock, or search
> the list first, then allocate, then search again.
> 
> Given that the not found case is vastly more common than the found
> case that doesn't seem to be worth the tradeoff.

Noted.