[PATCH] nvme-multipath: add an 'ana_groups_only' module option

[Christoph Hellwig]

On Wed, Feb 09, 2022 at 09:52:45PM -0500, John Meneghini wrote:
> I agree with Christoph.  I don't see the point in supporting 65536 
> namespaces across 49 ana groups or controllers. The problem here is: the 
> vendor is trying to turn NVMe into SCSI.

I'm not saying we should not support it.  We can trivially do that by
using a vmalloc buffer.  I don't think we should optimize for it, and
we certainly should not break behaviour which I think this does.

>
> Moreover, I don't understand how implementing this as a MODULE_PARM is 
> supposed to work.  If you configure this module parameter on it assumes all 
> NVMe-oF arrays connected to the host support RGO. What's really needed here 
> is some kind of protocol mechanism that will allow the host to dynamically 
> discovery if RGO is supported on a controller by controller basis.

RGO support is mandatory and has been there since the first released
ANA TP.