[dm-devel] [BUG] multipath-tools: uuid has become meaningless

[Hannes Reinecke]

Malahal Naineni wrote:
> Christophe Varoqui [christophe.varoqui at gmail.com] wrote:
>>    > 3. We could rename the devices instead of reload -- really fixing this!
>>    >
>>
>>    This one seems safe.
> 
> This is where I was heading. I did some investigation and found that we
> really need to rename to wwid based names before we finally rename to
> the intended name. So we may actually have two passes just to rename
> (first to wwid based names and then to actual names).  Also the current
> code doesn't do rename followed by reload even if it is needed. Someone
> sets friendly name and some other defaults that need reload like path
> grouping policy etc, we just rename! Probably a bug in itself.
> 
You sure? I would rather rely on device-mapper uuids here.
Point is that we
a) use 'mpath-<wwid>' as uuid for multipath generated tables anyway
and
b) uuids are a primary key for device-mapper, too.

So we can use the known naming scheme for the uuid to regenerate the
wwid; with this we can identify/access the device and we should be able to
make do with just one pass.

Two passes have the serious disadvantage of generating yet another set
of meaningless uevents, which then again have to be handled/ignored etc.

I'll be sending a patch to simplify dm_get_name() to illustrate my point.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
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