[PATCH] nvme-core: reduce io pause time when fail over

[Keith Busch]

On Wed, Jul 22, 2020 at 05:36:33PM +0800, Chao Leng wrote:
> To reduce io pause time, nvme_stop_queues use
> blk_mq_quiesce_queue_nowait to quiesce the queue, nvme_stop_queues wait
> all ongoing dispatches completed after all queues has been quiesced.

The comment above blk_mq_quiesce_queue_nowait() wants to remove this
function. I'm not sure we should be introducing more users if that's the
case.

Using synchronize_rcu() at the end may be looking to much into blk-mq's
internal quiesce implementation. It happens to be the right thing to do
for non-blocking hctx, so this patch assumes that will be true for any
nvme request_queue.