Re: [PATCH] BTT: Change nd_btt_arena_is_valid() to verify UUID

[Dan Williams]

On Fri, Dec 18, 2015 at 10:52 AM, Toshi Kani <toshi.kani@xxxxxxx> wrote:
> On Fri, 2015-12-18 at 09:54 -0800, Dan Williams wrote:
>> On Fri, Dec 18, 2015 at 7:15 AM, Toshi Kani <toshi.kani@xxxxxxx> wrote:
>> > On Fri, 2015-12-18 at 01:34 -0700, Vishal Verma wrote:
>> > > Also, I wonder if this problem is solved by using libndctl to manage
>> > > BTTs.
>> >
>> > I have not tested with libndctl yet, but I think our bind/unbind
>> > scripts do the same procedures.
>>
>> We loop through all combinations of sector size in our unit test.  If
>> you want to change the sector size the expectation is that the
>> namespace is destroyed and fully re-created, especially due to the
>> fact that changing sector size invalidates all data on the namespace.
>>
>> See: https://github.com/pmem/ndctl/blob/master/lib/test-libndctl.c
>
> The parent_uuid is not set on our NVDIMM-N systems.  I do not see 'uuid'
> file under sysfs 'namespaceX.X' per namespace_visible(), either.  This
> concept of creating/destroying a namespace is a bit foreign to us since
> we've never needed to do.  Can you elaborate how it's supposed to work for
> NVDIMM-N?
>

Ugh, yes.  An oversight on my part, let me give this some thought.
Whatever we decide, I want the libndctl api to be identical for the
two cases.

I expect the simplest option is to have
ndctl_namespace_disable_invalidate() destroy the btt-info block in the
NVDIMM-N case.
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