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

[Ewan Milne <emilne@redhat.com>]

alua_check_sense() checks for NOT READY / 04h 0Ah but not
UNIT ATTENTION with the same ASC/ASCQ.

Careful about updating pg->state in this case though because that
may cause subsequent I/O in the probe to fail, we didn't do this before
and we *may* only get the UA once.

-Ewan

On Wed, Sep 8, 2021 at 2:12 AM Hannes Reinecke <hare@suse.de> wrote:
>
> On 9/7/21 5:59 PM, michael.christie@oracle.com wrote:
> > On 9/7/21 2:16 AM, Hannes Reinecke 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.
> >>> Signed-off-by: Hannes Reinecke <hare@suse.de>
> >> ---
> >>   drivers/scsi/scsi_error.c | 7 ++++---
> >>   1 file changed, 4 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
> >> index 03a2ff547b22..1185083105ae 100644
> >> --- a/drivers/scsi/scsi_error.c
> >> +++ b/drivers/scsi/scsi_error.c
> >> @@ -594,10 +594,11 @@ enum scsi_disposition scsi_check_sense(struct scsi_cmnd *scmd)
> >>                  sshdr.asc == 0x3f && sshdr.ascq == 0x0e)
> >>                      return NEEDS_RETRY;
> >>              /*
> >> -             * if the device is in the process of becoming ready, we
> >> -             * should retry.
> >> +             * if the device is in the process of becoming ready, or
> >> +             * transitions between ALUA states, we should retry.
> >>               */
> >> -            if ((sshdr.asc == 0x04) && (sshdr.ascq == 0x01))
> >> +            if ((sshdr.asc == 0x04) &&
> >> +                (sshdr.ascq == 0x01 || sshdr.ascq == 0x0a))
> >>                      return NEEDS_RETRY;
> >
> > Why put this here instead of in alua_check_sense with the other ALUA
> > state transition check?
> >
> Good point. Will be updating the patch.
>
> Cheers,
>
> Hannes
> --
> Dr. Hannes Reinecke                Kernel Storage Architect
> hare@suse.de                              +49 911 74053 688
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