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

[Meneghini, John]

   On 11/23/20, 10:27 AM, "Knight, Frederick" <Frederick.Knight at netapp.com> wrote:

    Christoph claims that the ANA AEN should be send before the NS Attribute Changed AEN.  And, that could be true for an ANAGRPID 
    that changed (although, I don't see text describing any precedence or order requirements for delivery of AENs), but the NS creation
    case is explicitly excluded.  FWIW – Christoph was one of the people that requested this exclusion to prevent spaming the host with
    multiple AENs for the same event (a NS create).

An existing ANAGRPID which changes on an attached namespace should not produce an NVME_AEN_CFG_NS_ATTR AEN.  It produces an 
NVME_AEN_CFG_ANA_CHANGE AEN.  This is covered in: 

>  Namespace Attribute Changed: A controller shall not send this event if: b) the ANAGRPID field (refer to Figure 114) has changed;

  - and -

>  The Asymmetric Namespace Access information (refer to section 5.14.1.12) related to an ANA Group that contains namespaces attached to this controller
> has changed (e.g., an ANA state has changed, an ANAGRPID has changed). 

Although, I remember agreeing with Christoph that Linux would not support the "ANAGRPID has changed" AEN.

/John