Re: [PATCH] nvme: Use first ctrl->instance id as subsystem id

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On 14/08/2019 13:06, Keith Busch wrote:
> On Wed, Aug 14, 2019 at 07:28:36AM -0700, Guilherme G. Piccoli wrote:
>>[...]
> 
> The subsystem lifetime is not tied to a single controller's. Disconnect
> the "first" controller in a multipathed subsystem with this patch, then
> connect another controller from a different subsystem, and now you will
> create naming collisions.
> 

Hi Keith, thanks for your clarification. Isn't the controller id unique?
Could the new connected controller from a different subsystem have the
same id? If you can give a rough example I appreciate.

But given the above statement is a fact, what do you think of trying the
ctrl->instance first and in case we have duplicity, fallback to
subsystem ID allocator?

Since the creation of subsystems is not a critical path, adding this
small burden shouldn't be a huge penalty, and it'll help a lot with the
huge amount of reports of "confusion" after the introduction of nvme
multipathing, also it helps for the case I mentioned in the description,
some multipath'ed controllers, some single ones.

Cheers,


Guilherme



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