Re: [PATCH v4] I/O errors for ALUA state transitions

[Mike Christie <michael.christie@oracle.com>]

On 5/8/24 5:24 AM, Martin Wilck wrote:
> From: Rajashekhar M A <rajs@netapp.com>
> 
> When a host is configured with a few LUNs and IO is running,
> injecting FC faults repeatedly leads to path recovery problems.
> The LUNs have 4 paths each and 3 of them come back active after
> say an FC fault which makes two of the paths go down, instead of
> all 4. This happens after several iterations of continuous FC faults.
> 
> Reason here is that we're returning an I/O error whenever we're
> encountering sense code 06/04/0a (LOGICAL UNIT NOT ACCESSIBLE,
> ASYMMETRIC ACCESS STATE TRANSITION) instead of retrying.
> 
> mwilck: Moved this code to alua_check_sense() as suggested by
> Mike Christie [1]. Evan Milne had raised the question whether pg->state
> should be set to transitioning in the UA case [2]. I believe that doing
> this is correct. SCSI_ACCESS_STATE_TRANSITIONING by itself doesn't cause
> I/O errors. Our handler schedules an RTPG, which will only result in
> an I/O error condition if the transitioning timeout expires.
> 
> [1] https://lore.kernel.org/all/0bc96e82-fdda-4187-148d-5b34f81d4942@oracle.com/
> [2] https://lore.kernel.org/all/CAGtn9r=kicnTDE2o7Gt5Y=yoidHYD7tG8XdMHEBJTBraVEoOCw@mail.gmail.com/
> 
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Martin Wilck <mwilck@suse.com>
> Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
> ---


Reviewed-by: Mike Christie <michael.christie@oracle.com>