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Commit a8e5a2d5 authored by Stewart, Sean's avatar Stewart, Sean Committed by James Bottomley
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[SCSI] scsi_dh_alua: ALUA handler attach should succeed while TPG is transitioning 



During testing, it was discovered that when a device tries to attach to the
alua handler while in TPG state of transitioning, the alua_rtpg function will
wait for it to exit the state before allowing it to continue. As a result, if
the 60 second timeout expires, the alua handler will not attach to the device.

To fix this, I have introduced an input argument to alua_rtpg called
wait_for_transition.  The idea is that it will wait for the transition to
complete before an activation (because the current TPG state has some bearing
in that case), but during a discovery if it is transitioning, it will not
wait, and will store the state as standby for the time being.

I believe the precedent exists for this from commit
c0d289b3 Since if the device reports a state
of transitioning, it can transition to other more valid states, and it has
been established TPGS is supported on the device, if it is attaching.

Signed-off-by: default avatarSean Stewart <Sean.Stewart@netapp.com>
Acked-by: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarJames Bottomley <JBottomley@Parallels.com>
parent c20ee7b5

drivers/scsi/device_handler/scsi_dh_alua.c

+16 −10
Original line number Diff line number Diff line
@@ -522,12 +522,13 @@ static int alua_check_sense(struct scsi_device *sdev, 
/*

 * alua_rtpg - Evaluate REPORT TARGET GROUP STATES

 * @sdev: the device to be evaluated.

 * @wait_for_transition: if nonzero, wait ALUA_FAILOVER_TIMEOUT seconds for device to exit transitioning state

 *

 * Evaluate the Target Port Group State.

 * Returns SCSI_DH_DEV_OFFLINED if the path is

 * found to be unusable.

 */

static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)

static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_for_transition)

{

	struct scsi_sense_hdr sense_hdr;

	int len, k, off, valid_states = 0;
@@ -599,7 +600,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h) 
	else

		h->transition_tmo = ALUA_FAILOVER_TIMEOUT;



	if (orig_transition_tmo != h->transition_tmo) {

	if (wait_for_transition && (orig_transition_tmo != h->transition_tmo)) {

		sdev_printk(KERN_INFO, sdev,

			    "%s: transition timeout set to %d seconds\n",

			    ALUA_DH_NAME, h->transition_tmo);
@@ -637,14 +638,19 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h) 


	switch (h->state) {

	case TPGS_STATE_TRANSITIONING:

		if (wait_for_transition) {

			if (time_before(jiffies, expiry)) {

				/* State transition, retry */

				interval += 2000;

				msleep(interval);

				goto retry;

			}

		/* Transitioning time exceeded, set port to standby */

			err = SCSI_DH_RETRY;

		} else {

			err = SCSI_DH_OK;

		}



		/* Transitioning time exceeded, set port to standby */

		h->state = TPGS_STATE_STANDBY;

		break;

	case TPGS_STATE_OFFLINE:
@@ -678,7 +684,7 @@ static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h) 
	if (err != SCSI_DH_OK)

		goto out;



	err = alua_rtpg(sdev, h);

	err = alua_rtpg(sdev, h, 0);

	if (err != SCSI_DH_OK)

		goto out;
@@ -738,7 +744,7 @@ static int alua_activate(struct scsi_device *sdev, 
	int err = SCSI_DH_OK;

	int stpg = 0;



	err = alua_rtpg(sdev, h);

	err = alua_rtpg(sdev, h, 1);

	if (err != SCSI_DH_OK)

		goto out;