dm-thin: free devices after block manager

Free devices after block manager. The block manager may access the device
on termination, so we must not close the device prematurely.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

Index: linux-3.0-fast/drivers/md/dm-thin.c
===================================================================
--- linux-3.0-fast.orig/drivers/md/dm-thin.c	2011-08-14 18:22:22.000000000 +0200
+++ linux-3.0-fast/drivers/md/dm-thin.c	2011-08-14 18:24:11.000000000 +0200
@@ -1425,10 +1425,12 @@ static void pool_dtr(struct dm_target *t
 {
 	struct pool_c *pt = ti->private;
 
-	dm_put_device(ti, pt->metadata_dev);
-	dm_put_device(ti, pt->data_dev);
 	unbind_control_target(pt->pool, ti);
 	pool_dec(pt->pool);
+
+	dm_put_device(ti, pt->metadata_dev);
+	dm_put_device(ti, pt->data_dev);
+
 	kfree(pt);
 }