sorting out the freeze / quiesce mess

[Ming Lei]

On Wed, Nov 10, 2021 at 10:14:07AM +0100, Christoph Hellwig wrote:
> Hi Jens and Ming,
> 
> I've been looking into properly supporting queue freezing for bio based
> drivers (that is only release q_usage_counter on bio completion for them).
> And the deeper I look into the code the more I'm confused by us having
> the blk_mq_quiesce* interface in addition to blk_freeze_queue.  What
> is a good reason to do a quiesce separately from a freeze?

freeze can make sure that all requests are done, quiesce can make sure that
dispatch critical area(covered by hctx lock/unlock) is done.


Thanks,
Ming