[PATCH 1/1] mid-layer unblocks blocked sdev leaving queue stopped

[Michael Reed <mdr@sgi.com>]

scsi_add_lun() and scsi_sysfs_add_sdev() unconditionally set the sdev
state to SDEV_RUNNING.  If this sdev was blocked via scsi_internal_device_block()
the changing of the state to running will result in the device's queue
remaining stopped after the call to scsi_internal_device_unblock() and
commands becoming stuck.  This patch changes scsi_add_lun() and
scsi_sysfs_add_sdev() to not move the sdev to running if it is
blocked. It leaves it to the blocker of the sdev to unblock it.

Found during large lun count testing using 13 FC host adapter ports.
In my testing the sdev was blocked due to disruptions or events on the
fibre channel link.

Signed-off-by: Michael Reed <mdr@sgi.com>

==

--- a/drivers/scsi/scsi_sysfs.c	2009-12-16 16:26:14.512882449 -0600
+++ scsi-misc/drivers/scsi/scsi_sysfs.c	2009-12-16 16:23:33.352882975 -0600
@@ -878,8 +878,14 @@ int scsi_sysfs_add_sdev(struct scsi_devi
 	struct request_queue *rq = sdev->request_queue;
 	struct scsi_target *starget = sdev->sdev_target;
 
-	if ((error = scsi_device_set_state(sdev, SDEV_RUNNING)) != 0)
-		return error;
+	/*
+	 * If device is blocked, leave state alone and let
+	 * blocker unblock when appropriate.
+	 */
+	if (sdev->sdev_state != SDEV_BLOCK) {
+		if ((error = scsi_device_set_state(sdev, SDEV_RUNNING)) != 0)
+			return error;
+	}
 
 	error = scsi_target_add(starget);
 	if (error)
--- a/drivers/scsi/scsi_scan.c	2009-12-16 16:26:14.512882449 -0600
+++ scsi-misc/drivers/scsi/scsi_scan.c	2009-12-16 16:25:58.084976675 -0600
@@ -902,17 +902,22 @@ static int scsi_add_lun(struct scsi_devi
 	if (*bflags & BLIST_USE_10_BYTE_MS)
 		sdev->use_10_for_ms = 1;
 
-	/* set the device running here so that slave configure
-	 * may do I/O */
-	ret = scsi_device_set_state(sdev, SDEV_RUNNING);
-	if (ret) {
-		ret = scsi_device_set_state(sdev, SDEV_BLOCK);
-
+	/*
+	 * If device is blocked, leave state alone and let blocker
+	 * unblock when appropriate.  Otherwise, set the device
+	 * running here so that slave configure may perform i/o.
+	 */
+	if (sdev->sdev_state != SDEV_BLOCK) {
+		ret = scsi_device_set_state(sdev, SDEV_RUNNING);
 		if (ret) {
-			sdev_printk(KERN_ERR, sdev,
+			ret = scsi_device_set_state(sdev, SDEV_BLOCK);
+
+			if (ret) {
+				sdev_printk(KERN_ERR, sdev,
 				    "in wrong state %s to complete scan\n",
 				    scsi_device_state_name(sdev->sdev_state));
-			return SCSI_SCAN_NO_RESPONSE;
+				return SCSI_SCAN_NO_RESPONSE;
+			}
 		}
 	}