[PATCH v5 1/2] blk-mq: add tagset quiesce interface

[Sagi Grimberg]

> I like the tagset based interface.

Even that we need to unquiesce back the connect_q?
See my comment on v5. Kinda bothers me...

   But the idea of doing a per-hctx
> allocation and wait doesn't seem very scalable.

I belong to this camp too..

> Paul, do you have any good idea for an interface that waits on
> multiple srcu heads?  As far as I can tell we could just have a single
> global completion and counter, and each call_srcu would just just
> decrement it and then the final one would do the wakeup.  It would just
> be great to figure out a way to keep the struct rcu_synchronize and
> counter on stack to avoid an allocation.
> 
> But if we can't do with an on-stack object I'd much rather just embedd
> the rcu_head in the hw_ctx.