[dm-devel] [RFC PATCH v2 0/3] add library to check if device is a valid path

[Martin Wilck]

On Wed, 2020-09-23 at 23:59 -0500, Benjamin Marzinski wrote:
> The main part of the this patchset is the first patch, which adds a
> new library interface to check whether devices are valid paths. This
> was designed for use in the Storage Instantiation Daemon (SID).
> 
> https://github.com/sid-project
> 
> Hopefully, I've removed all the controvertial bits from the last time
> I
> proposed this library.
> 
> The second patch adds get_uid fallback code for dasd devices. The
> third
> patch just changes the get_uid log level for devices configured with
> uid_attribute "". This is because it is currently necessary to
> configure
> multipath with
> 
> overrides {
>         uid_attribute ""
> }
> 
> to claim multipath devices with SID (instead of using
> multipath.rules),
> since SID doesn't currently get the UID information itself, and it is
> called by udev before this information is added to the udev database.
> 

This makes me wonder how SID and multipathd are supposed to coexist.
We wouldn't want this overrides directive for multipathd itself, would
we?

Actually that "overrides" begs for allowing a custom configuration file
for libmultipath to be used with SID. OTOH, that would allow the
configurations to diverge, which might cause issues, too (in particular
if blacklisting options were different).

I think what we should do is allow applications to set overrides like
this at runtime, modifying the configuration. Perhaps we could support
an application-specific, additional config_dir, from which items like
the above could be read in addition to the regular configuration files.
This additional configuration would not be used by multipathd and
multipath. Does that make sense?

Regards
Martin

-- 
Dr. Martin Wilck <mwilck at suse.com>, Tel. +49 (0)911 74053 2107
SUSE  Software Solutions Germany GmbH
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Imendörffer