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Commit 9d2c3039 authored by Hannes Reinecke's avatar Hannes Reinecke Committed by Martin K. Petersen
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scsi_dh_alua: Send TEST UNIT READY to poll for transitioning 



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.

Reviewed-by: default avatarBart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: default avatarEwan Milne <emilne@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent c57168a1

drivers/scsi/device_handler/scsi_dh_alua.c

+38 −0
Original line number Diff line number Diff line
@@ -465,6 +465,30 @@ static int alua_check_sense(struct scsi_device *sdev, 
	return SCSI_RETURN_NOT_HANDLED;

}



/*

 * 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 occurred, 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.
@@ -732,8 +756,22 @@ static void alua_rtpg_work(struct work_struct *work) 
		alua_wq = kaluad_sync_wq;

	pg->flags |= ALUA_PG_RUNNING;

	if (pg->flags & ALUA_PG_RUN_RTPG) {

		int state = pg->state;



		pg->flags &= ~ALUA_PG_RUN_RTPG;

		spin_unlock_irqrestore(&pg->lock, flags);

		if (state == TPGS_STATE_TRANSITIONING) {

			if (alua_tur(sdev) == SCSI_DH_RETRY) {

				spin_lock_irqsave(&pg->lock, flags);

				pg->flags &= ~ALUA_PG_RUNNING;

				pg->flags |= ALUA_PG_RUN_RTPG;

				spin_unlock_irqrestore(&pg->lock, flags);

				queue_delayed_work(alua_wq, &pg->rtpg_work,

						   pg->interval * HZ);

				return;

			}

			/* Send RTPG on failure or if TUR indicates SUCCESS */

		}

		err = alua_rtpg(sdev, pg);

		spin_lock_irqsave(&pg->lock, flags);

		if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {