Upstream patch:
https://www.redhat.com/archives/lvm-devel/2009-August/msg00106.html

# ===================================================================
# RCS file: /cvs/lvm2/LVM2/WHATS_NEW,v
# retrieving revision 1.1241
# retrieving revision 1.1242
# diff -u -r1.1241 -r1.1242
# --- LVM2/WHATS_NEW	2009/08/13 17:16:38	1.1241
# +++ LVM2/WHATS_NEW	2009/08/19 15:34:33	1.1242
# @@ -1,5 +1,6 @@
#  Version 2.02.52 -
#  =================================
# +  Fix pvcreate on a partition (2.02.51).
#    Fix vgcfgrestore error paths when locking fails (2.02.49).
#    Added configure --enable-clogd to conditionally build the cluster log daemon.
#    Make lvchange --refresh only take a read lock on volume group.
# ===================================================================
# RCS file: /cvs/lvm2/LVM2/lib/device/dev-md.c,v
# retrieving revision 1.18
# retrieving revision 1.19
diff -u -r1.18 -r1.19
--- LVM2/lib/device/dev-md.c	2009/08/01 17:14:52	1.18
+++ LVM2/lib/device/dev-md.c	2009/08/19 15:34:43	1.19
@@ -137,13 +137,15 @@
 	if (!sysfs_dir || !*sysfs_dir)
 		return ret;
 
-check_md_major:
-	if (MAJOR(dev) != md_major()) {
-		if (get_primary_dev(sysfs_dir, blkdev, &dev))
-			goto check_md_major;
-		return ret;
+	if (MAJOR(dev) == blkext_major()) {
+		/* lookup parent MD device from blkext partition */
+		if (!get_primary_dev(sysfs_dir, blkdev, &dev))
+			return ret;
 	}
 
+	if (MAJOR(dev) != md_major())
+		return ret;
+
 	ret = dm_snprintf(path, size, "%s/dev/block/%d:%d/md/%s", sysfs_dir,
 			  (int)MAJOR(dev), (int)MINOR(dev), attribute);
 	if (ret < 0) {
===================================================================
RCS file: /cvs/lvm2/LVM2/lib/filters/filter.c,v
retrieving revision 1.48
retrieving revision 1.49
diff -u -r1.48 -r1.49
--- LVM2/lib/filters/filter.c	2009/07/09 22:34:02	1.48
+++ LVM2/lib/filters/filter.c	2009/08/19 15:34:46	1.49
@@ -38,6 +38,7 @@
 } device_info_t;
 
 static int _md_major = -1;
+static int _blkext_major = -1;
 static int _device_mapper_major = -1;
 
 int md_major(void)
@@ -45,6 +46,11 @@
 	return _md_major;
 }
 
+int blkext_major(void)
+{
+	return _blkext_major;
+}
+
 /*
  * Devices are only checked for partition tables if their minor number
  * is a multiple of the number corresponding to their type below
@@ -197,6 +203,10 @@
 		if (!strncmp("md", line + i, 2) && isspace(*(line + i + 2)))
 			_md_major = line_maj;
 
+		/* Look for blkext device */
+		if (!strncmp("blkext", line + i, 6) && isspace(*(line + i + 6)))
+			_blkext_major = line_maj;
+
 		/* Look for device-mapper device */
 		/* FIXME Cope with multiple majors */
 		if (!strncmp("device-mapper", line + i, 13) && isspace(*(line + i + 13)))
===================================================================
RCS file: /cvs/lvm2/LVM2/lib/filters/filter.h,v
retrieving revision 1.15
retrieving revision 1.16
diff -u -r1.15 -r1.16
--- LVM2/lib/filters/filter.h	2007/08/20 20:55:25	1.15
+++ LVM2/lib/filters/filter.h	2009/08/19 15:34:46	1.16
@@ -36,6 +36,7 @@
 void lvm_type_filter_destroy(struct dev_filter *f);
 
 int md_major(void);
+int blkext_major(void);
 int max_partitions(int major);
 
 #endif