[PATCH 1/2] nvme: make NVMe freeze API reliably

[Ming Lei]

On Thu, Aug 25, 2022 at 06:02:33PM +0800, Chao Leng wrote:
> 
> 
> On 2022/8/21 16:47, Ming Lei wrote:
> > From: Keith Busch <kbusch at kernel.org>
> > 
> > In some corner cases[1], freeze wait and unfreeze API may be called on
> > unfrozen queue, add one per-ns flag of NVME_NS_FREEZE to make these
> > freeze APIs more reliably, then this kind of issues can be avoided.
> > And similar approach has been applied on stopping/quiescing nvme queues.
> This leads to another problem: the process that needs to be
> in the frozen state is not actually frozen.
> It's not safe.

The flag is just to control if queue wait is needed, blk_mq_freeze_queue_wait
can be done only the flag is set. Not sure how it isn't safe.

Meantime calling blk_mq_freeze_queue_wait() on queue not being started
to freeze is usually a bug, and I think WARN_ON_ONCE() can be added
in nvme_wait_freeze().


Thanks,
Ming