Re: Behavior with duplicate UUID's

[Scott Talbert <talbert@techie.net>]

On Mon, 9 Aug 2010, Kay Sievers wrote:

> The behavior is undefined, and can only be controlled with
> link_priority= option.
>
> We can't, and don't want to pretend to make any control over 'the
> first one'. In a hotplug world, there is almost never a correct first
> one, because everything runs in parallel.

I agree with you that if two devices are hotplugged at around the same 
time, the result would be expectedly unpredictable.  However, if you have 
your root partition (with a symlink established at bootup), and then hours 
later, you hotplug another device, it would seem to me that the symlink of 
the older device would be preferable to keep.  Right now, the symlink for 
the original device is removed and a symlink for the new one is added.

I propose a slightly different change.  This changes the symlink priority 
processing when the priorities are the same.  The oldest symlink is 
instead preferred, rather than the newest one.

--- udev-node.c.orig	2010-05-20 11:06:52.000000000 -0400
+++ udev-node.c	2010-08-10 22:52:53.000000000 -0400
@@ -261,9 +261,10 @@

  			devnode = udev_device_get_devnode(dev_db);
  			if (devnode != NULL) {
-				dbg(udev, "compare priority of '%s'(%i) > '%s'(%i)\n", target, priority,
-				    udev_device_get_devnode(dev_db), udev_device_get_devlink_priority(dev_db));
-				if (target = NULL || udev_device_get_devlink_priority(dev_db) > priority) {
+				dbg(udev, "compare priority of '%s'(%i) >= '%s'(%i)\n",
+				    udev_device_get_devnode(dev_db), udev_device_get_devlink_priority(dev_db),
+				    target, priority);
+				if (target = NULL || udev_device_get_devlink_priority(dev_db) >= priority) {
  					info(udev, "'%s' claims priority %i for '%s'\n",
  					     udev_device_get_syspath(dev_db), udev_device_get_devlink_priority(dev_db), stackdir);
  					priority = udev_device_get_devlink_priority(dev_db);

---

Thanks,
Scott