From: Chris Lalancette <clalance@redhat.com>
Date: Thu, 17 Jul 2008 17:28:45 +0200
Subject: [xen] don't try to recreate sysfs entries
Message-id: 487F652D.8090904@redhat.com
O-Subject: [RHEL5.3 PATCH 4/7]: Don't try to recreate sysfs entries v2
Bugzilla: 250104
RH-Acked-by: Stephen Tweedie <sct@redhat.com>
RH-Acked-by: Bill Burns <bburns@redhat.com>
RH-Acked-by: Don Dutile <ddutile@redhat.com>

This patch makes sure that tap_update_blkif_status() does not fail to update
statistics because it fails to re-create existing sysfs entries.  From
xen-3.1-testing.hg c/s 15078

diff --git a/drivers/xen/blktap/xenbus.c b/drivers/xen/blktap/xenbus.c
index a9a9c2b..38dbcb3 100644
--- a/drivers/xen/blktap/xenbus.c
+++ b/drivers/xen/blktap/xenbus.c
@@ -161,7 +161,9 @@ int xentap_sysfs_addif(struct xenbus_device *dev)
 
 void xentap_sysfs_delif(struct xenbus_device *dev)
 {
+	struct backend_info *be = dev->dev.driver_data;
 	sysfs_remove_group(&dev->dev.kobj, &tapstat_group);
+	be->group_added = 0;
 }
 
 static int blktap_remove(struct xenbus_device *dev)
@@ -212,11 +214,13 @@ static void tap_update_blkif_status(blkif_t *blkif)
 		return;
 	}
 
-	err = xentap_sysfs_addif(blkif->be->dev);
-	if (err) {
-		xenbus_dev_fatal(blkif->be->dev, err, 
-				 "creating sysfs entries");
-		return;
+	if (!blkif->be->group_added) {
+		err = xentap_sysfs_addif(blkif->be->dev);
+		if (err) {
+			xenbus_dev_fatal(blkif->be->dev, err, 
+					 "creating sysfs entries");
+			return;
+		}
 	}
 
 	blkif->xenblkd = kthread_run(tap_blkif_schedule, blkif, name);