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

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

On Mon, 2015-04-27 at 11:35 +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.
> 
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> ---
>  drivers/scsi/sd.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index 79beebf..7178b05 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -1987,6 +1987,11 @@ static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
>  				 * give it one more chance */
>  				if (--reset_retries > 0)
>  					continue;
> +			if (sense_valid &&
> +			    sshdr.sense_key == NOT_READY &&
> +			    sshdr.asc == 0x04 && sshdr.ascq == 0x0A)
> +				/* ALUA state transition; always retry */
> +				continue;
>  		}
>  		retries--;
>  
> @@ -2069,6 +2074,11 @@ static int read_capacity_10(struct scsi_disk *sdkp, struct scsi_device *sdp,
>  				 * give it one more chance */
>  				if (--reset_retries > 0)
>  					continue;
> +			if (sense_valid &&
> +			    sshdr.sense_key == NOT_READY &&
> +			    sshdr.asc == 0x04 && sshdr.ascq == 0x0A)
> +				/* ALUA state transition; always retry */
> +				continue;
>  		}
>  		retries--;
>  

Got to say I really don't like this infinite retry possibility.  How
long does the ALUA transition take?  Would increasing retries work (or
even hijacking reset_retries)?

James