Re: [PATCH] sd: always retry READ CAPACITY for ALUA state transition

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Tue, 2017-10-17 at 09:11 +0200, Hannes Reinecke wrote:
> During ALUA state transitions the device might return
> a sense code 02/04/0a (Logical unit not accessible, asymmetric
> access state transition). As this is a transient error
> we should just retry the READ CAPACITY call until
> the state transition finishes and the correct
> capacity can be returned.

This will lock up the system if some ALUA initiator gets into a state
where it always returns transitioning and never completes, which
doesn't look like the best way to handle problem devices.

I thought after the ALUA transition the LUN gives a unit attention ...
can't you use that some way to trigger the capacity re-read, so do
asynchronous event notification instead of polling forever.

James