On Thu, 2015-08-27 at 14:41 +0200, Hannes Reinecke wrote:
> Sending a 'REPORT TARGET PORT GROUP' command is a costly operation,
> as the array has to gather information about all ports.
> So instead of using RTPG to poll for a status update when a port
> is in transitioning we should be sending a TEST UNIT READY, and
> wait for the sense code to report success.
>
> Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
> ---
> drivers/scsi/device_handler/scsi_dh_alua.c | 33 ++++++++++++++++++++++++++++++
> 1 file changed, 33 insertions(+)
>
> diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
> index 2fa985e..3c6b365 100644
> --- a/drivers/scsi/device_handler/scsi_dh_alua.c
> +++ b/drivers/scsi/device_handler/scsi_dh_alua.c
> @@ -467,6 +467,30 @@ static int alua_check_sense(struct scsi_device *sdev,
> }
>
> /*
> + * alua_tur - Send a TEST UNIT READY
> + * @sdev: device to which the TEST UNIT READY command should be send
> + *
> + * Send a TEST UNIT READY to @sdev to figure out the device state
> + * Returns SCSI_DH_RETRY if the sense code is NOT READY/ALUA TRANSITIONING,
> + * SCSI_DH_OK if no error occured, and SCSI_DH_IO otherwise.
> + */
> +static int alua_tur(struct scsi_device *sdev)
> +{
> + struct scsi_sense_hdr sense_hdr;
> + int retval;
> +
> + retval = scsi_test_unit_ready(sdev, ALUA_FAILOVER_TIMEOUT * HZ,
> + ALUA_FAILOVER_RETRIES, &sense_hdr);
> + if (sense_hdr.sense_key == NOT_READY &&
> + sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
> + return SCSI_DH_RETRY;
> + else if (retval)
> + return SCSI_DH_IO;
> + else
> + return SCSI_DH_OK;
> +}
> +
> +/*
> * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
> * @sdev: the device to be evaluated.
> *
> @@ -725,7 +749,16 @@ static void alua_rtpg_work(struct work_struct *work)
> return;
> }
> if (pg->flags & ALUA_PG_RUN_RTPG) {
> + int state = pg->state;
> spin_unlock_irqrestore(&pg->rtpg_lock, flags);
> + if (state == TPGS_STATE_TRANSITIONING) {
> + if (alua_tur(sdev) == SCSI_DH_RETRY) {
> + queue_delayed_work(pg->work_q, &pg->rtpg_work,
> + pg->interval * HZ);
> + return;
> + }
> + /* Send RTPG on failure or if TUR indicates SUCCESS */
> + }
> err = alua_rtpg(sdev, pg);
> if (err == SCSI_DH_RETRY) {
> queue_delayed_work(pg->work_q, &pg->rtpg_work,
Reviewed-by: Ewan D. Milne <emilne@xxxxxxxxxx>
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