[PATCH 3/5] blk-mq: add helper of blk_mq_global_quiesce_wait()

[Sagi Grimberg]

>>> Add helper of blk_mq_global_quiesce_wait() for supporting to quiesce
>>> queues in parallel, then we can just wait once if global quiesce wait
>>> is allowed.
>>
>> blk_mq_global_quiesce_wait() is a poor name... global is scope-less and
>> obviously it has a scope.
> 
> How about blk_mq_shared_quiesce_wait()? or any suggestion?

Shared between what?

Maybe if the queue has a non-blocking tagset, it can have a "quiesced"
flag that is cleared in unquiesce? then the callers can just continue
to iterate but will only wait the rcu grace period once.