[dm-devel] [PATCH 04/18] retrigger uevents to try and get the uid through udev

[Hannes Reinecke]

On 10/08/2015 09:44 PM, Benjamin Marzinski wrote:
> Ideally, udev will be able to grab the wwid when a path device is
> discovered, but sometimes this isn't possible. In these cases, the
> best thing that could happen would be for udev to actually get the
> information, and add it to its database. This patch makes multipath
> retrigger uevents a limited number of times before giving up and
> trying to get the information itself.
> 
> There are two configurables that control how it does this,
> "retrigger_tries" and "retrigger_delay". The first sets the number of
> times it will try to retrigger a uevent to get the wwid, the second
> sets the amount of time to wait between retriggers.
> 
> This patch currently only tries reinitializing the path on change events
> after multipathd has triggered a change event, and it only tries once
> per triggered change event.  Now, its possible that other change events
> could occur on the device without multipathd tirggering them.  As the
> patch stands now, it won't try to initialize the device on those.  It will,
> however still try in the checkerloop, but only after it has finished
> retriggering the uevents. We could be much more aggressive here, and assume
> that devices that simply won't have a WWID should already be taken care of
> by the blacklists, so it would be always a good idea to recheck devices on
> change events. What would be ideal is if udev would let us know when it had
> problems or timed out when processing a uevent, so we would know if
> retriggering the uevent would be useful.
> 
> Signed-off-by: Benjamin Marzinski <bmarzins at redhat.com>
> ---
Hmm. Yes, this 'udev killing worker after a certain time' is a major
pain. And we've tried to work around it, too.
With various degrees of success.
But I'm not sure if retriggering is a good idea here; we simply have
no idea if the failure is legit or not.

Can't we work with the udev/systemd folks to add a variable telling
us that udev killed the worker?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		               zSeries & Storage
hare at suse.de			               +49 911 74053 688
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