libnvdimm, pfn: fix uuid validation

BugLink: http://bugs.launchpad.net/bugs/1573034

commit e5670563 upstream.

If we detect a namespace has a stale info block in the init path, we
should overwrite with the latest configuration.  In fact, we already
return -ENODEV when the parent uuid is invalid, the same should be done
for the 'self' uuid.  Otherwise we can get into a condition where
userspace is unable to reconfigure the pfn-device without directly /
manually invalidating the info block.
Reported-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/nvdimm/pfn_devs.c

@@ -275,7 +275,7 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn)
 	} else {
 		/* from init we validate */
 		if (memcmp(nd_pfn->uuid, pfn_sb->uuid, 16) != 0)
-			return -EINVAL;
+			return -ENODEV;
 	}
 
 	/*