On Thu, 2020-09-24 at 20:08 -0500, Benjamin Marzinski wrote: > On Thu, Sep 24, 2020 at 07:22:21PM +0000, Martin Wilck wrote: > > > > So, SID will call into libmultipath via libmpathvalid, udev will > > obtain > > the properties from SID, and multipathd will fetch them from udev > > in > > turn? Or will multipathd talk directly to SID? I seem to be missing > > the > > overall picture. > > Yeah. SID will populate the udev database with the necessary udev > properties, and multipathd will get those udev properties just like > it > always does. But then I'm not getting how you'll get along with a SID-specific configuration for libmultipath's behavior. You want get_uid() to use direct sysfs access for SID, and use udev for multipath(d). How else would you achieve that? More generally, I'm not quite convinced of the the design yet. The information flow kernel -> (sysfs or ioctl) -> libmultipath(sid mode) -> libmpathvalid -> SID -> udev -> udev db -> libudev -> libmultipath (udev mode) -> multipathd is more complex than it needs to be. It might actually increase the lags experienced by multipathd, which will still have to wait for uevent workers to finish until it can be certain about device properties. Not to mention that SID must be rock stable and always available during boot, initrd processing, etc. Why don't we rather write a common library for determining WWIDs and the "should be multipathed" predicate, to be used by udev (with a plugin), multipath-tools, SID, and possibly other tools like systemd and LVM, with common, simple configuration, guaranteed to always provide the same results? I mean, libmultipath already has all the "intelligence" built-in to do this. We'd "just" need to cut down configuration options drastically to get more reprocucible results, and refactor things to obtain a minimalistic API. Unlike the current libmpathvalid design, this wouldn't be built on top of current libmultipath, rather vice-versa. multipath-tools would also benefit a lot from such work. Regards Martin -- Dr. Martin Wilck <mwilck@xxxxxxxx>, Tel. +49 (0)911 74053 2107 SUSE Software Solutions Germany GmbH HRB 36809, AG Nürnberg GF: Felix Imendörffer -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
