Re: [PATCH] Consider namespace with size as active namespace

["Verma, Vishal L" <vishal.l.verma@intel.com>]

On Thu, 2019-10-17 at 08:35 +0530, Aneesh Kumar K.V wrote:
> 
> > > ---
> > >   ndctl/namespace.c | 3 ++-
> > >   1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/ndctl/namespace.c b/ndctl/namespace.c
> > > index 58a9e3c53474..1f212a2b3a9b 100644
> > > --- a/ndctl/namespace.c
> > > +++ b/ndctl/namespace.c
> > > @@ -455,7 +455,8 @@ static int is_namespace_active(struct ndctl_namespace *ndns)
> > >   	return ndns && (ndctl_namespace_is_enabled(ndns)
> > >   		|| ndctl_namespace_get_pfn(ndns)
> > >   		|| ndctl_namespace_get_dax(ndns)
> > > -		|| ndctl_namespace_get_btt(ndns));
> > > +		|| ndctl_namespace_get_btt(ndns)
> > > +		|| ndctl_namespace_get_size(ndns));
> > >   }
> > >   
> > >   /*
[..]
> 
> > The failing unit tests are sector-mode.sh and dax.sh
> > 
> 
> I will see if i can run them on ppc64. We still had issues in getting 
> ndctl check to be running on ppc64.
> 

I dug into this a bit more.

The failure happens on 'legacy' namespaces (ND_DEVICE_NAMESPACE_IO).

There is an assumption that legacy namespaces cannot be fully deleted,
so as part of a reconfigure, when it comes time to delete the namespace
(ndctl_namespace_delete()), we refuse to do that, and bail, before
setting the size to zero.

libndctl.c:4467

	case ND_DEVICE_NAMESPACE_BLK:
		break;
	default:
		dbg(ctx, "%s: nstype: %d not deletable\n",
				ndctl_namespace_get_devname(ndns),
				ndctl_namespace_get_type(ndns));
		return 0;
	}

	rc = namespace_set_size(ndns, 0);
...

Indeed, destroy namespace wouldn't even get to that point, because that
assumption is repeated in namespace_destroy(), where we switch on
namespace type, and potentially skip over the ndctl_namespace_destroy
call entirely.

If setting the size to zero is now significant we'd need to rework both
of these sites. In destroy_namespace(), delay the did_zero checking
until after ndctl_namespace_delete(), and in ndctl_namespace_delete(),
set the size to zero before the type check.

Dan, does the above make sense - was there reason to refrain from
touching the size on legacy namespaces?

	-Vishal
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