From: Richard Jones <rjones@redhat.com>
Subject: [RHEL5.1 PATCH] race between loading xenblk.ko and scanning for LVM partitions etc.
Date: Fri, 20 Jul 2007 13:25:36 -0400
Bugzilla: 247265
Message-Id: <46A0F010.5080201@redhat.com>
Changelog: [xen] race loading xenblk.ko and scanning for LVM partitions


Don Zickus wrote:
>On Fri, Jul 13, 2007 at 10:49:12AM +0100, Richard W.M. Jones wrote:
>>https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=247265
>>
>>The attached patch is the upstream Xen fix which fixes this race 
>>condition, just modified so it applies cleanly to 2.6.18-32.el5.
>>
>>Rich.
>
--- linux-2.6.18.x86_64/drivers/xen/blkfront/blkfront.c	2007-07-13 10:34:31.000000000 +0100
+++ linux-2.6.18.x86_64/drivers/xen/blkfront/blkfront.c	2007-07-13 10:35:14.000000000 +0100
@@ -340,6 +340,8 @@
 	spin_unlock_irq(&blkif_io_lock);
 
 	add_disk(info->gd);
+
+	info->is_ready = 1;
 }
 
 /**
@@ -815,6 +817,13 @@
 	spin_unlock_irq(&blkif_io_lock);
 }
 
+int blkfront_is_ready(struct xenbus_device *dev)
+{
+	struct blkfront_info *info = dev->dev.driver_data;
+
+	return info->is_ready;
+}
+
 
 /* ** Driver Registration ** */
 
@@ -833,6 +842,7 @@
 	.remove = blkfront_remove,
 	.resume = blkfront_resume,
 	.otherend_changed = backend_changed,
+	.is_ready = blkfront_is_ready,
 };
 
 
--- linux-2.6.18.x86_64/drivers/xen/blkfront/block.h	2007-07-13 10:34:31.000000000 +0100
+++ linux-2.6.18.x86_64/drivers/xen/blkfront/block.h	2007-07-13 10:36:01.000000000 +0100
@@ -124,6 +124,7 @@
 	struct gnttab_free_callback callback;
 	struct blk_shadow shadow[BLK_RING_SIZE];
 	unsigned long shadow_free;
+	int is_ready;
 
 	/**
 	 * The number of people holding this device open.  We won't allow a
--- linux-2.6.18.x86_64/drivers/xen/xenbus/xenbus_probe.c	2007-07-13 10:34:31.000000000 +0100
+++ linux-2.6.18.x86_64/drivers/xen/xenbus/xenbus_probe.c	2007-07-13 10:35:14.000000000 +0100
@@ -1100,6 +1100,7 @@
 {
 	struct xenbus_device *xendev = to_xenbus_device(dev);
 	struct device_driver *drv = data;
+	struct xenbus_driver *xendrv;
 
 	/*
 	 * A device with no driver will never connect. We care only about
@@ -1112,7 +1113,9 @@
 	if (drv && (dev->driver != drv))
 		return 0;
 
-	return (xendev->state != XenbusStateConnected);
+	xendrv = to_xenbus_driver(dev->driver);
+	return (xendev->state != XenbusStateConnected ||
+		(xendrv->is_ready && !xendrv->is_ready(xendev)));
 }
 
 static int exists_disconnected_device(struct device_driver *drv)
--- linux-2.6.18.x86_64/include/xen/xenbus.h	2007-07-13 10:34:31.000000000 +0100
+++ linux-2.6.18.x86_64/include/xen/xenbus.h	2007-07-13 10:35:14.000000000 +0100
@@ -104,6 +104,7 @@
 	int (*uevent)(struct xenbus_device *, char **, int, char *, int);
 	struct device_driver driver;
 	int (*read_otherend_details)(struct xenbus_device *dev);
+	int (*is_ready)(struct xenbus_device *dev);
 };
 
 static inline struct xenbus_driver *to_xenbus_driver(struct device_driver *drv)