[PATCH 6/6] nvme: track shared namespaces in a siblings list

[hch@lst.de (Christoph Hellwig)]

On Mon, Jun 19, 2017@02:27:26PM +0300, Sagi Grimberg wrote:
> I completely agree that the multipath map (sibling list) is
> driver specific, I'm just arguing that the search itself can
> be invoked from the block layer through a block_device_operation
> when the bdev is created (in there, the driver sibling search has
> its own driver specific locking).

Let's wait for that until we have some block layer code posted.
I'll see if I can make this work, but I suspect driving the search
from the driver is going to be a lot easier.

> btw, I didn't see handling of the case where a sibling match found where
> the sibling is already linked (a sibling too).
>
> say we have namespaces a, b and c, where b,c are siblings of a (all with
> the same nsid=3).
>
> If I read the code correctly, c will link to both a and b wouldn't it?
>
> Do we need to check: list_empty(&cur->siblings)?
>
> Or am I not understanding the data structure?

Yeah, we should break after finding the first sibling.  Let me create
a test setup with three controllers with the same namespaces..