initialise the bvec dp properly.
--- diff/drivers/md/dm-io.c	2004-02-18 09:13:08.000000000 +0000
+++ source/drivers/md/dm-io.c	2004-02-18 09:18:18.000000000 +0000
@@ -428,6 +428,8 @@
 
 void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
 {
+	dp->get_page = bvec_get_page;
+	dp->next_page = bvec_next_page;
 	dp->context_ptr = bvec;
 }