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

[Keith Busch]

On Fri, Nov 20, 2020 at 10:44:32AM +0100, hch at lst.de wrote:
> 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.

That sequence would have a group with no namespaces, which I is okay,
but we can tolerant targets that don't use that sequence without much
difficulty. This ought to do it:

---
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 74896be40c17..300cff8c616d 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -667,6 +667,8 @@ void nvme_mpath_add_disk(struct nvme_ns *ns, struct nvme_id_ns *id)
 		if (desc.state) {
 			/* found the group desc: update */
 			nvme_update_ns_ana_state(&desc, ns);
+		} else {
+			nvme_read_ana_log(ctrl);
 		}
 	} else {
 		ns->ana_state = NVME_ANA_OPTIMIZED; 
--