[PATCH 5/6] blk-mq: Fix queue freeze deadlock

[Sagi Grimberg]

> If hardware queues are stopped for some event, like the device has been
> suspended by power management, requests allocated on that hardware queue
> are indefinitely stuck causing a queue freeze to wait forever.

I have a problem with this patch. IMO, this is a general issue so, so
why do we tie a fix to calling blk_mq_update_nr_hw_queues()? We might
not need to update nr_hw_queues at all. I'm fine with the
blk_mq_abandon_stopped_requests but not with its call-site.

Usually a driver knows when it wants to abandon all busy requests
blk_mq_tagset_busy_iter(), maybe the right approach is to add
a hook for all allocated tags? Or have blk_mq_quisce_queue get a
fail all requests parameter from the callers?