vgname_from_mda now tries to parse for vgname even

if rlocn not defined (there is no metadata area).

In most cases it fails in validate_name(),
unfortunately there are situatuions, when
validate_name is ok and later code fails with
checksum error.

Reproducer:

# dd if=/dev/zero of=/dev/loop0

# pvcreate --metadatasize 637k /dev/loop0
  Physical volume "/dev/loop0" successfully created

# pvs /dev/loop0
  /dev/loop0: Checksum error
      PV         VG   Fmt  Attr PSize PFree
        /dev/loop0      lvm2 --   1.00M 1.00M

Signed-off-by: Milan Broz <mbroz@redhat.com>

-

lib/format_text/format-text.c

@@ -1061,6 +1061,12 @@ const char *vgname_from_mda(const struct format_type *fmt,
 	/* FIXME Cope with returning a list */
 	rlocn = mdah->raw_locns;
 
+	/*
+	 * If no valid offset, do not try to search for vgname
+	 */
+	if (!rlocn->offset)
+		goto out;
+
 	/* Do quick check for a vgname */
 	if (!dev_read(dev_area->dev, dev_area->start + rlocn->offset,
 		      NAME_LEN, buf))