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

[Keith Busch]

On Wed, Aug 24, 2022 at 01:15:28PM +0200, Hannes Reinecke wrote:
> On 8/21/22 10:47, Ming Lei wrote:
> > @@ -5065,8 +5073,10 @@ void nvme_start_freeze(struct nvme_ctrl *ctrl)
> >   	struct nvme_ns *ns;
> >   	down_read(&ctrl->namespaces_rwsem);
> > -	list_for_each_entry(ns, &ctrl->namespaces, list)
> > +	list_for_each_entry(ns, &ctrl->namespaces, list) {
> > +		set_bit(NVME_NS_FREEZE, &ns->flags);
> 
> Why not test_and_set_bit()?
> Which would have the nice effect of adding a memory barrier ...

Sure, I think you can even make a new WARN if the test fails. It should never
fail in this path, otherwise we could mess up the freeze depth.