[dm-devel] User friendly names patch.

[Christophe Varoqui]

> > One of my worry is that /var/lib/multipath/bindings is not available in
> > early userspace. Is this taken care of. Also remember not relying on
> > hotplug to execute multipath in early userspace is a redhat choice.
> > Others strategy may differ.
> 
> To make this work seamlessly with early userspace, You would need to add
> the correct /var/lib/multipath/bindings file to the initrd. The easiest work
> around to to simply stick the alias for that device in /etc/multipath.conf.
> 
> To make this work without editing the initrd or forcing people to have
> aliases in their config files, you would need to change multipath behavior.
> Currently, if multipath finds a device with the same wwid and a different
> alias, it removes the device and recreates it.  If it simply just left the
> device with the old name, then you would not get the benefit of user friendly
> names for devices that were started in early userspace, but you would not
> be any worse off than before. (Well, not quite. A binding would exist for the
> device in the bindings file, and if on some other boot, that multipath wasn't
> created in early userspace, when it got created it would use the name from
> the bindings file). This method would also require a command line option to
> override the "user_friendly_names" config file option in early userspace.
> 
ok,

let me know what you think of the following early userspace scenario sketch.
It aleviates the bindings sync issues between early and normal userspace.

Pre-requisites :
- no multipath config or binding files packaged in early userspace
- move bindings from /var to /etc

early userspace trace :
- load storage drivers
- path nodes are created
- lookup the rootdev wwid in a config file created at system install time or
  by init{ramfs,rd} rebuild script
- exec "multipath $wwid" : the scope limiting is the trick as only root dev
  map gets created. All defaults will apply : failover policy, etc ...
- mount /dev/mapper/$wwid
- pump config and bindings in early userspace namespace
- umount root fs
- exec "multipath $wwid" again
- deduce $alias from {bindings file & $wwid}
- mount /dev/mapper/$alias

Regards,
cvaroqui