[SCSI] fix our current target reap infrastructure

This patch eliminates the reap_ref and replaces it with a proper kref.
On last put of this kref, the target is removed from visibility in
sysfs.  The final call to scsi_target_reap() for the device is done from
__scsi_remove_device() and only if the device was made visible.  This
ensures that the target disappears as soon as the last device is gone
rather than waiting until final release of the device (which is often
too long).

Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable@vger.kernel.org # delay backport by 2 months for field testing
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 14 insertions, 6 deletions

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 9117d0bf408e..665acbf83693 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -383,17 +383,14 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
 {
 	struct scsi_device *sdev;
 	struct device *parent;
-	struct scsi_target *starget;
 	struct list_head *this, *tmp;
 	unsigned long flags;
 
 	sdev = container_of(work, struct scsi_device, ew.work);
 
 	parent = sdev->sdev_gendev.parent;
-	starget = to_scsi_target(parent);
 
 	spin_lock_irqsave(sdev->host->host_lock, flags);
-	starget->reap_ref++;
 	list_del(&sdev->siblings);
 	list_del(&sdev->same_target_siblings);
 	list_del(&sdev->starved_entry);
@@ -413,8 +410,6 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
 	/* NULL queue means the device can't be used */
 	sdev->request_queue = NULL;
 
-	scsi_target_reap(scsi_target(sdev));
-
 	kfree(sdev->inquiry);
 	kfree(sdev);
 
@@ -1071,6 +1066,13 @@ void __scsi_remove_device(struct scsi_device *sdev)
 		sdev->host->hostt->slave_destroy(sdev);
 	transport_destroy_device(dev);
 
+	/*
+	 * Paired with the kref_get() in scsi_sysfs_initialize().  We have
+	 * remoed sysfs visibility from the device, so make the target
+	 * invisible if this was the last device underneath it.
+	 */
+	scsi_target_reap(scsi_target(sdev));
+
 	put_device(dev);
 }
 
@@ -1133,7 +1135,7 @@ void scsi_remove_target(struct device *dev)
 			continue;
 		if (starget->dev.parent == dev || &starget->dev == dev) {
 			/* assuming new targets arrive at the end */
-			starget->reap_ref++;
+			kref_get(&starget->reap_ref);
 			spin_unlock_irqrestore(shost->host_lock, flags);
 			if (last)
 				scsi_target_reap(last);
@@ -1217,6 +1219,12 @@ void scsi_sysfs_device_initialize(struct scsi_device *sdev)
 	list_add_tail(&sdev->same_target_siblings, &starget->devices);
 	list_add_tail(&sdev->siblings, &shost->__devices);
 	spin_unlock_irqrestore(shost->host_lock, flags);
+	/*
+	 * device can now only be removed via __scsi_remove_device() so hold
+	 * the target.  Target will be held in CREATED state until something
+	 * beneath it becomes visible (in which case it moves to RUNNING)
+	 */
+	kref_get(&starget->reap_ref);
 }
 
 int scsi_is_sdev_device(const struct device *dev)