[PATCH] nvme-core: update NS Attr Changed AEN handling for ANA group

[hch at lst.de]

On Wed, Nov 18, 2020 at 08:09:43PM +0000, George, Martin wrote:
> > How can the namespace reference an ANA group that we haven't been
> > notified about using the NVME_AEN_CFG_ANA_CHANGE AEN before?
> 
> Well, I think that could be possible for a newly created namespace,
> which happens to belong to a new ANA group. To quote the 1.4 spec in
> context of Asymmetric Namespace Access Change under the Asynchronous
> Event Information - Notice (Figure 147):
> 
> "A controller shall not send this event if:
> a) the change is due to the creation of a namespace (refer to section
> 5.20); or
> b) the change is due to the deletion of a namespace (refer to section
> 5.20),
> as the Namespace Attribute Changed event is sent for these changes."
> 
> So it looks the NVME_AEN_CFG_ANA_CHANGE AEN is not required here for
> such cases, but instead the NVME_AEN_CFG_NS_ATTR AEN would do.

For the newly created namespace to beong to a newly created ANA group
the controller first needs to send NVME_AEN_CFG_ANA_CHANGE to announce
the ANA group, it then send NVME_AEN_CFG_NS_ATTR to announce the
new namespaces.  But the new namespace can't reference an ANA group
that didn't exist, that is a separate event.