Re: [PATCH] scsi_dh_alua: handle RTPG sense code correctly during state transitions

[Laurence Oberman <loberman@redhat.com>]

On Mon, 2019-10-07 at 15:57 +0200, Hannes Reinecke wrote:
> From: Hannes Reinecke <hare@suse.com>
> 
> Some arrays are not capable of returning RTPG data during state
> transitioning, but rather return an 'LUN not accessible, asymmetric
> access state transition' sense code. In these cases we
> can set the state to 'transitioning' directly and don't need to
> evaluate the RTPG data (which we won't have anyway).
> 
> Signed-off-by: Hannes Reinecke <hare@suse.com>
> ---
>  drivers/scsi/device_handler/scsi_dh_alua.c | 21 ++++++++++++++++--
> ---
>  1 file changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c
> b/drivers/scsi/device_handler/scsi_dh_alua.c
> index 4971104b1817..f32da0ca529e 100644
> --- a/drivers/scsi/device_handler/scsi_dh_alua.c
> +++ b/drivers/scsi/device_handler/scsi_dh_alua.c
> @@ -512,6 +512,7 @@ static int alua_rtpg(struct scsi_device *sdev,
> struct alua_port_group *pg)
>  	unsigned int tpg_desc_tbl_off;
>  	unsigned char orig_transition_tmo;
>  	unsigned long flags;
> +	bool transitioning_sense = false;
>  
>  	if (!pg->expiry) {
>  		unsigned long transition_tmo = ALUA_FAILOVER_TIMEOUT *
> HZ;
> @@ -572,13 +573,19 @@ static int alua_rtpg(struct scsi_device *sdev,
> struct alua_port_group *pg)
>  			goto retry;
>  		}
>  		/*
> -		 * Retry on ALUA state transition or if any
> -		 * UNIT ATTENTION occurred.
> +		 * If the array returns with 'ALUA state transition'
> +		 * sense code here it cannot return RTPG data during
> +		 * transition. So set the state to 'transitioning'
> directly.
>  		 */
>  		if (sense_hdr.sense_key == NOT_READY &&
> -		    sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
> -			err = SCSI_DH_RETRY;
> -		else if (sense_hdr.sense_key == UNIT_ATTENTION)
> +		    sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a) {
> +			transitioning_sense = true;
> +			goto skip_rtpg;
> +		}
> +		/*
> +		 * Retry on any other UNIT ATTENTION occurred.
> +		 */
> +		if (sense_hdr.sense_key == UNIT_ATTENTION)
>  			err = SCSI_DH_RETRY;
>  		if (err == SCSI_DH_RETRY &&
>  		    pg->expiry != 0 && time_before(jiffies, pg-
> >expiry)) {
> @@ -666,7 +673,11 @@ static int alua_rtpg(struct scsi_device *sdev,
> struct alua_port_group *pg)
>  		off = 8 + (desc[7] * 4);
>  	}
>  
> + skip_rtpg:
>  	spin_lock_irqsave(&pg->lock, flags);
> +	if (transitioning_sense)
> +		pg->state = SCSI_ACCESS_STATE_TRANSITIONING;
> +
>  	sdev_printk(KERN_INFO, sdev,
>  		    "%s: port group %02x state %c %s supports
> %c%c%c%c%c%c%c\n",
>  		    ALUA_DH_NAME, pg->group_id, print_alua_state(pg-
> >state),

This makes sense to me and has affected recovery timeouts in the past.
Code looks correct to me. 

Reviewed-by: Laurence Oberman <loberman@redhat.com>