scsi_dh_alua: ALUA handler attach should succeed while TPG is transitioning

PATCH RESEND In review Stewart, Sean 2 participants 2 messages Oct 15, 2013 – Oct 16, 2013 SCSI

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Stewart, Sean

author

2013-10-15 15:52 UTC #0 lore raw

PATCH RESEND 2/2 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 c0d289b3e59577532c45ee9110ef81bd7b341272 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 Sean Stewart <[email protected]>

---
 drivers/scsi/device_handler/scsi_dh_alua.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

drivers/scsi/device_handler/scsi_dh_alua.c +16 ~~-10~~

index 78205cc..5248c88 100644
@@ -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 (time_before(jiffies, expiry)) {
-			/* State transition, retry */
-			interval += 2000;
-			msleep(interval);
-			goto retry;
+		if (wait_for_transition) {
+			if (time_before(jiffies, expiry)) {
+				/* State transition, retry */
+				interval += 2000;
+				msleep(interval);
+				goto retry;
+			}
+			err = SCSI_DH_RETRY;
+		} else {
+			err = SCSI_DH_OK;
 		}
+
 		/* Transitioning time exceeded, set port to standby */
-		err = SCSI_DH_RETRY;
 		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;

Signature · 1 line

1.8.3.1

Hannes Reinecke

Acked-by on v1 2/2

2013-10-16 05:49 UTC #1 lore raw

Quoted 10 lines · Sean

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.

Quoted 5 lines

I believe the precedent exists for this from commit c0d289b3e59577532c45ee9110ef81bd7b341272 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 Sean Stewart <[email protected]>

Hmm. Looks like you're correct.

Acked-by Hannes Reinecke <[email protected]>

Cheers,

Hannes

Signature · 8 lines

Dr. Hannes Reinecke		      zSeries & Storage
[email protected]			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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