[dm-devel] [PATCH] libmultipath: Use existing user friendly name if possible

[Bryn M. Reeves]

On Fri, Mar 28, 2014 at 09:01:14PM +0000, Stewart, Sean wrote:
> When a system is booted to the SAN, a condition can occur where one
> user friendly name is given to a disk during boot, but multipathd tries
> to allocate a different one after boot. If the second alias is already
> used by another device, multipathd can't rename it. Multipathd then has
> incorrect information about the alias/wwid relationships, which can
> result in paths being added to the wrong map.

This should only happen if the initramfs and root file system have
inconsistent multipath configurations (either multipath.conf or bindings
/ wwids file mismatched). That's not really a valid configuration for
the system to be in and leads to the type of problems you describe.

> This patch works around this problem by first trying to use the alias
> already bound to a device during boot.  If the bindings file has that
> alias bound to a different device, it'll auto generate a new alias to
> rename it to.

To be honest I'd prefer to see this cause an error. These types of
configurations currently run the risk of silent data corruption - I'd
much rather deal with a system that refuses to boot due to an out of
date initramfs image than one that quietly remaps paths in unexpected
ways.

Regards,
Bryn.