Re: [PATCH 2/2] scsi: Handle power-on reset unit attention

[Ewan Milne <emilne@redhat.com>]

On Thu, 2014-06-05 at 09:26 +0200, Hannes Reinecke wrote:
> As per SAM there is a status precedence, with any sense code 29/XX
> taking second place just after an ACA ACTIVE status.
> Additionally, each target might prefer to not queue any unit
> attention conditions but just report one.
> Due to the above this will be that one with the highest precedence.
> This results in the sense code 29/XX effectively overwriting any
> other unit attention.
> Hence we should report the power-on reset to userland so that
> it can take appropriate action.
> 
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> ---
>  drivers/scsi/scsi_error.c  | 6 ++++++
>  drivers/scsi/scsi_lib.c    | 4 ++++
>  include/scsi/scsi_device.h | 3 ++-
>  3 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
> index 47a1ffc..65ed333 100644
> --- a/drivers/scsi/scsi_error.c
> +++ b/drivers/scsi/scsi_error.c
> @@ -420,6 +420,12 @@ static void scsi_report_sense(struct scsi_device *sdev,
>  				    "threshold.\n");
>  		}
>  
> +		if (sshdr->asc == 0x29) {
> +			evt_type = SDEV_EVT_POWER_ON_RESET_OCCURRED;
> +			sdev_printk(KERN_WARNING, sdev,
> +				    "Power-on or device reset occurred\n");
> +		}
> +
>  		if (sshdr->asc == 0x2a && sshdr->ascq == 0x01) {
>  			evt_type = SDEV_EVT_MODE_PARAMETER_CHANGE_REPORTED;
>  			sdev_printk(KERN_WARNING, sdev,
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 9f841df..ee158c1 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -2183,6 +2183,9 @@ static void scsi_evt_emit(struct scsi_device *sdev, struct scsi_event *evt)
>  	case SDEV_EVT_LUN_CHANGE_REPORTED:
>  		envp[idx++] = "SDEV_UA=REPORTED_LUNS_DATA_HAS_CHANGED";
>  		break;
> +	case SDEV_EVT_POWER_ON_RESET_OCCURRED:
> +		envp[idx++] = "SDEV_UA=POWER_ON_RESET_OCCURRED";
> +		break;
>  	default:
>  		/* do nothing */
>  		break;
> @@ -2286,6 +2289,7 @@ struct scsi_event *sdev_evt_alloc(enum scsi_device_event evt_type,
>  	case SDEV_EVT_SOFT_THRESHOLD_REACHED_REPORTED:
>  	case SDEV_EVT_MODE_PARAMETER_CHANGE_REPORTED:
>  	case SDEV_EVT_LUN_CHANGE_REPORTED:
> +	case SDEV_EVT_POWER_ON_RESET_OCCURRED:
>  	default:
>  		/* do nothing */
>  		break;
> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
> index 5853c91..7b9a886 100644
> --- a/include/scsi/scsi_device.h
> +++ b/include/scsi/scsi_device.h
> @@ -57,9 +57,10 @@ enum scsi_device_event {
>  	SDEV_EVT_SOFT_THRESHOLD_REACHED_REPORTED,	/* 38 07  UA reported */
>  	SDEV_EVT_MODE_PARAMETER_CHANGE_REPORTED,	/* 2A 01  UA reported */
>  	SDEV_EVT_LUN_CHANGE_REPORTED,			/* 3F 0E  UA reported */
> +	SDEV_EVT_POWER_ON_RESET_OCCURRED,		/* 29 00  UA reported */
>  
>  	SDEV_EVT_FIRST		= SDEV_EVT_MEDIA_CHANGE,
> -	SDEV_EVT_LAST		= SDEV_EVT_LUN_CHANGE_REPORTED,
> +	SDEV_EVT_LAST		= SDEV_EVT_POWER_ON_RESET_OCCURRED,
>  
>  	SDEV_EVT_MAXBITS	= SDEV_EVT_LAST + 1
>  };

This looks fine to me.  We might want to figure out a way
to report the ASCQ in an environment variable on this uevent,
since there are multiple sub-cases:

29 00 D POWER ON, RESET, OR BUS DEVICE RESET OCCURRED
29 01 D POWER ON OCCURRED
29 02 D SCSI BUS RESET OCCURRED
29 03 D BUS DEVICE RESET FUNCTION OCCURRED
29 04 D DEVICE INTERNAL RESET
29 05 D TRANSCEIVER MODE CHANGED TO SINGLE-ENDED
29 06 D TRANSCEIVER MODE CHANGED TO LVD
29 07 D I_T NEXUS LOSS OCCURRED

...but we could add that in a subsequent patch.

A related problem is that when this UA is received, the
device may have changed some of its attributes, so some
of the information that the mid-layer caches may be stale.
The udev rule handling this event should probably rescan
the device.

Reviewed-by: Ewan D. Milne <emilne@redhat.com>