Re: [ndctl RFC PATCH] ndctl/namespace: create namespaces greedily

From: "Verma, Vishal L" <vishal.l.verma@intel.com>
To: "Williams, Dan J" <dan.j.williams@intel.com>,
	"Scargall, Steve" <steve.scargall@intel.com>
Cc: "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>
Subject: Re: [ndctl RFC PATCH] ndctl/namespace: create namespaces greedily
Date: Wed, 28 Aug 2019 23:17:01 +0000	[thread overview]
Message-ID: <9f412408dfb12a69767b5034435776a5853eb64f.camel@intel.com> (raw)
In-Reply-To: <507921D13093A64EAF066075F3F6ED13076E4922@ORSMSX111.amr.corp.intel.com>

On Wed, 2019-08-28 at 15:38 -0700, Scargall, Steve wrote:
> Thanks for the clarification.  I have a much better understanding
> now. 
> 
> Updating the ndctl-create-namespace man page to clarify what '
> --region=all' does and does not do in combination with other arguments
> and options would be beneficial.   This would actually provide a more
> immediate solution to the problem.  It sounds like the general
> statement used in the other man pages can remain?  Or are there other
> exceptions?

Yep I have a patch clarifying the --region option for create-namespace.
'all' is used in two ways, --<object>=all  or ndctl-<action> all.

The former acts as a filter, where as the latter acts as a "act on all"
directive.

So 'ndctl disable-namespace --region=region0 all' disables all
namespaces on region0, where as
'ndctl disable-namespace --region=all all' is the same as omitting the
--region option (while still acceptable syntax), and acts on all
namespaces regardless of the region.

> 
> With the proposed implementation that bails out on first error, `
> --continue` seems reasonable vs. `--greedy`.  What do you think about
> `--all-regions` instead?  It is more meaningful towards its intended
> action or use-case, but would it cause confusion with `
> --regions=all`?   Documentation could provide the solution here.  We
> would have to choose an arbitrary short option since `-a` and `-r` are
> already taken.  

I prefer --continue/-c since it automatically extends to buses as well.
As a result, with these changes, 'ndctl create-namespace -c' will create
namespaces on all possible regions on all possible buses.

> 
> Whatever the final decision, we should test for and return a usage
> error for a mutually exclusive set of inputs, i.e. `ndctl create-
> namespace --all-regions --region=region0` doesn't make sense - either
> you want to perform the create operation on all regions or only in
> region0.

With --continue this isn't a big problem as the --region restriction
will render the --continue meaningless.
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