Re: [PATCH v2] driver/nvme/host: Support duplicated nsid for the private ns

[Sagi Grimberg]

> > > +static struct nvme_ns_head *nvme_find_ns_head(struct nvme_ctrl *ctrl,
> > >    		unsigned nsid)
> > >    {
> > > +	struct nvme_subsystem *subsys = ctrl->subsys;
> > >    	struct nvme_ns_head *h;
> > >      	lockdep_assert_held(&subsys->lock);
> >
> > IMO it is a bit strange that we now don't pass in the subsystem but
> > require that the subsys->lock is taken...
>
> We do things like that in various places, mostly because information
> needed that is subsystem-wide hangs of the nvme_ctrl structure, in
> this case the various feature bitmaps.  We could move them to the
> subsystem structure, which would be the right thing to do but a fair
> amout of churn for little savings.

Yea I understand its not universally enforced, just popped up.

> > > +++ b/drivers/nvme/host/multipath.c
> > > @@ -504,10 +504,11 @@ int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl, struct nvme_ns_head *head)
> > >      	/*
> > >    	 * Add a multipath node if the subsystems supports multiple controllers.
> > > -	 * We also do this for private namespaces as the namespace sharing data could
> > > -	 * change after a rescan.
> > > +	 * We also do this for private namespaces as the namespace sharing flag
> > > +	 * could change after a rescan.
> >
> > What happens in this case? we now have non-unique shared namespaces?
>
> The non-uniqueue NSIDs can only happen for private namespaces.

But what happens if this changes upon a rescan as you commented?