[Bug 644489] Re: constantly changes /dev/disk/by-id/{scsi, wwn}-* LUN symlinks with multipathing

[Serge Hallyn]

Hi Peter,

I assigned this to you to get your feedback.  To summarize this bug,
the line

# Coalesce multipath devices before multipathd is running (initramfs, early
# boot)
ACTION=="add|change", SUBSYSTEM=="block", RUN+="/sbin/multipath -v0 /dev/%k"

in 95-multipath.tools udev rule was added to:

multipath-tools (0.4.8-11) unstable; urgency=low
[...]
  * [4f8a5d1] Call multipath via udev on block device add/change events This
    helps slow devices when either /etc/init.d/multipath-tools-boot or the
    initramfs script are being run although the devices are not ready yet.
    (Closes: #489850) - many thanks to Janusz Dziemidowicz for his suggestions
    and testing
[...]

However, for some reason calling 'multipath -v0 /dev/sdb' for this user
causes udev to fire off a changed rule for /dev/sdb, triggering this
rule, causing multipath to be called, etc.

My first suggestion is that we keep this rule only for 'add' but not for
'change'.  Having it for 'change' doesn't seem to meet the reasons why
it was originally aded.

Secondly, should we drop this rule altogether and just make sure to
load scsi_wait_scan and then do udevsettle?  Or will that miss devices
which magically show up later (but not too late)?

(Please feel free to assign to me after commenting)

** Changed in: multipath-tools (Ubuntu)
     Assignee: (unassigned) => Peter Petrakis (peter-petrakis)

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https://bugs.launchpad.net/bugs/644489

Title:
  constantly changes /dev/disk/by-id/{scsi,wwn}-* LUN symlinks with
  multipathing